From 2cfe4748e57bd510b98ca81bd915f801f5a50bb5 Mon Sep 17 00:00:00 2001
From: Rui Abreu Ferreira <raf-ep@gmx.com>
Date: Sun, 9 Jun 2019 18:22:10 +0100
Subject: [PATCH 1/6] provider: let providers decide their status

Instead of deciding provider status in eval_has_provider, move the
decision to the provider Vim scripts.

Previously, provider loading worked as follows:

1. eval_has_provider() verified provider availability by searching for
   the provider#providername#Call function and cached this verificaion as a static
   variable for some providers
2. providers short-circuited on loading to prevent the definition of the
   Call function (with the exception of the node provider that did not)

This commit changes the expected interface between nvim and its
providers to facilitate provider reloading, by splitting the
verification of the provider from the availability of the Call function.

eval_has_provider() now checks for a provider#providername#enabled
variable. It is up to the provider script to set this to 0 or 1
accordingly. eval_call_provider() remains unchanged.

All providers hosting a Call function were updated to respect this.

The clipboard provider now has a Reload function to reload the
provider.
---
 runtime/autoload/provider/clipboard.vim       | 16 ++++--
 runtime/autoload/provider/node.vim            |  4 ++
 runtime/autoload/provider/python.vim          |  6 +-
 runtime/autoload/provider/python3.vim         |  6 +-
 runtime/autoload/provider/ruby.vim            |  3 +
 runtime/doc/develop.txt                       |  6 +-
 src/nvim/eval.c                               | 55 +++++--------------
 .../fixtures/autoload/provider/brokencall.vim |  2 +
 .../autoload/provider/brokenenabled.vim       |  6 ++
 .../fixtures/autoload/provider/clipboard.vim  |  1 +
 test/functional/provider/provider_spec.lua    | 19 +++++++
 11 files changed, 65 insertions(+), 59 deletions(-)
 create mode 100644 test/functional/fixtures/autoload/provider/brokencall.vim
 create mode 100644 test/functional/fixtures/autoload/provider/brokenenabled.vim
 create mode 100644 test/functional/provider/provider_spec.lua

diff --git a/runtime/autoload/provider/clipboard.vim b/runtime/autoload/provider/clipboard.vim
index 2b06ee8c48..e43f8fbb7a 100644
--- a/runtime/autoload/provider/clipboard.vim
+++ b/runtime/autoload/provider/clipboard.vim
@@ -48,6 +48,9 @@ endfunction
 let s:cache_enabled = 1
 let s:err = ''
 
+" eval_has_provider checks the variable to verify provider status
+let g:provider#clipboard#enabled = 0
+
 function! provider#clipboard#Error() abort
   return s:err
 endfunction
@@ -120,12 +123,11 @@ function! provider#clipboard#Executable() abort
   return ''
 endfunction
 
-if empty(provider#clipboard#Executable())
-  " provider#clipboard#Call() *must not* be defined if the provider is broken.
-  " Otherwise eval_has_provider() thinks the clipboard provider is
-  " functioning, and eval_call_provider() will happily call it.
-  finish
-endif
+" Call this to setup/reload the provider
+function! provider#clipboard#Reload()
+  " #enabled is used by eval_has_provider()
+  let g:provider#clipboard#enabled = !empty(provider#clipboard#Executable())
+endfunction
 
 function! s:clipboard.get(reg) abort
   if type(s:paste[a:reg]) == v:t_func
@@ -192,3 +194,5 @@ function! provider#clipboard#Call(method, args) abort
     let s:here = v:false
   endtry
 endfunction
+
+call provider#clipboard#Reload()
diff --git a/runtime/autoload/provider/node.vim b/runtime/autoload/provider/node.vim
index 35882849bd..6413720605 100644
--- a/runtime/autoload/provider/node.vim
+++ b/runtime/autoload/provider/node.vim
@@ -2,6 +2,7 @@ if exists('g:loaded_node_provider')
   finish
 endif
 let g:loaded_node_provider = 1
+let g:provider#node#enabled = 0
 
 function! s:is_minimum_version(version, min_major, min_minor) abort
   if empty(a:version)
@@ -143,6 +144,9 @@ let s:prog = provider#node#Detect()
 
 if empty(s:prog)
   let s:err = 'Cannot find the "neovim" node package. Try :checkhealth'
+else
+  let g:provider#node#enabled = 1
 endif
 
 call remote#host#RegisterPlugin('node-provider', 'node', [])
+
diff --git a/runtime/autoload/provider/python.vim b/runtime/autoload/provider/python.vim
index a06cbe4814..d65506a55a 100644
--- a/runtime/autoload/provider/python.vim
+++ b/runtime/autoload/provider/python.vim
@@ -10,6 +10,7 @@ endif
 let g:loaded_python_provider = 1
 
 let [s:prog, s:err] = provider#pythonx#Detect(2)
+let g:provider#python#enabled = !empty(s:prog)
 
 function! provider#python#Prog() abort
   return s:prog
@@ -19,11 +20,6 @@ function! provider#python#Error() abort
   return s:err
 endfunction
 
-if s:prog == ''
-  " Detection failed
-  finish
-endif
-
 " The Python provider plugin will run in a separate instance of the Python
 " host.
 call remote#host#RegisterClone('legacy-python-provider', 'python')
diff --git a/runtime/autoload/provider/python3.vim b/runtime/autoload/provider/python3.vim
index 242a224cb3..469611c7ce 100644
--- a/runtime/autoload/provider/python3.vim
+++ b/runtime/autoload/provider/python3.vim
@@ -10,6 +10,7 @@ endif
 let g:loaded_python3_provider = 1
 
 let [s:prog, s:err] = provider#pythonx#Detect(3)
+let g:provider#python3#enabled = !empty(s:prog)
 
 function! provider#python3#Prog() abort
   return s:prog
@@ -19,11 +20,6 @@ function! provider#python3#Error() abort
   return s:err
 endfunction
 
-if s:prog == ''
-  " Detection failed
-  finish
-endif
-
 " The Python3 provider plugin will run in a separate instance of the Python3
 " host.
 call remote#host#RegisterClone('legacy-python3-provider', 'python3')
diff --git a/runtime/autoload/provider/ruby.vim b/runtime/autoload/provider/ruby.vim
index 3b4c6c4839..df43dffa40 100644
--- a/runtime/autoload/provider/ruby.vim
+++ b/runtime/autoload/provider/ruby.vim
@@ -7,6 +7,7 @@ let g:loaded_ruby_provider = 1
 function! provider#ruby#Detect() abort
   return s:prog
 endfunction
+let g:provider#ruby#enabled = 0
 
 function! provider#ruby#Prog() abort
   return s:prog
@@ -65,6 +66,8 @@ let s:plugin_path = expand('<sfile>:p:h') . '/script_host.rb'
 
 if empty(s:prog)
   let s:err = 'Cannot find the neovim RubyGem. Try :checkhealth'
+else
+  let g:provider#ruby#enabled = 1
 endif
 
 call remote#host#RegisterClone('legacy-ruby-provider', 'ruby')
diff --git a/runtime/doc/develop.txt b/runtime/doc/develop.txt
index 843e23ee54..0f9e17e697 100644
--- a/runtime/doc/develop.txt
+++ b/runtime/doc/develop.txt
@@ -111,7 +111,7 @@ functions in eval.c:
 - eval_call_provider(name, method, arguments): calls provider#(name)#Call
   with the method and arguments.
 - eval_has_provider(name): Checks if a provider is implemented. Returns true
-  if the provider#(name)#Call function is implemented. Called by |has()|
+  if the provider#(name)#enabled variable is not 0. Called by |has()|
   (vimscript) to check if features are available.
 
 The provider#(name)#Call function implements integration with an external
@@ -119,8 +119,8 @@ system, because shell commands and |RPC| clients are easier to work with in
 vimscript.
 
 For example, the Python provider is implemented by the
-autoload/provider/python.vim script; the provider#python#Call function is only
-defined if a valid external Python host is found. That works well with the
+autoload/provider/python.vim script; the variable provider#python#enabled is only
+1 if a valid external Python host is found. That works well with the
 `has('python')` expression (normally used by Python plugins) because if the
 Python host isn't installed then the plugin will "think" it is running in
 a Vim compiled without the "+python" feature.
diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index cefd351dd7..ed01ca9f99 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -23968,52 +23968,27 @@ typval_T eval_call_provider(char *provider, char *method, list_T *arguments)
   return rettv;
 }
 
-bool eval_has_provider(const char *name)
+/// Check if a named provider is enabled
+bool eval_has_provider(const char *provider)
 {
-#define CHECK_PROVIDER(name) \
-  if (has_##name == -1) { \
-    has_##name = !!find_func((char_u *)"provider#" #name "#Call"); \
-    if (!has_##name) { \
-      script_autoload("provider#" #name "#Call", \
-                      sizeof("provider#" #name "#Call") - 1, \
-                      false); \
-      has_##name = !!find_func((char_u *)"provider#" #name "#Call"); \
-    } \
-  }
+  char enabled_varname[256];
+  int enabled_varname_len = snprintf(enabled_varname, sizeof(enabled_varname),
+                                     "provider#%s#enabled", provider);
 
-  static int has_clipboard = -1;
-  static int has_python = -1;
-  static int has_python3 = -1;
-  static int has_ruby = -1;
-  typval_T args[1];
-  args[0].v_type = VAR_UNKNOWN;
+  typval_T tv;
+  if (get_var_tv(enabled_varname, enabled_varname_len, &tv,
+                 NULL, false, false) == FAIL) {
+    char call_varname[256];
+    snprintf(call_varname, sizeof(call_varname), "provider#%s#Call", provider);
+    int has_call = !!find_func((char_u *)call_varname);
 
-  if (strequal(name, "clipboard")) {
-    CHECK_PROVIDER(clipboard);
-    return has_clipboard;
-  } else if (strequal(name, "python3")) {
-    CHECK_PROVIDER(python3);
-    return has_python3;
-  } else if (strequal(name, "python")) {
-    CHECK_PROVIDER(python);
-    return has_python;
-  } else if (strequal(name, "ruby")) {
-    bool need_check_ruby = (has_ruby == -1);
-    CHECK_PROVIDER(ruby);
-    if (need_check_ruby && has_ruby == 1) {
-      char *rubyhost = call_func_retstr("provider#ruby#Detect", 0, args, true);
-      if (rubyhost) {
-        if (*rubyhost == NUL) {
-          // Invalid rubyhost executable. Gem is probably not installed.
-          has_ruby = 0;
-        }
-        xfree(rubyhost);
-      }
+    if (has_call && p_lpl) {
+      emsgf("Provider '%s' failed to set %s", provider, enabled_varname);
     }
-    return has_ruby;
+    return false;
   }
 
-  return false;
+  return (tv.v_type == VAR_NUMBER) ? tv.vval.v_number != 0: true;
 }
 
 /// Writes "<sourcing_name>:<sourcing_lnum>" to `buf[bufsize]`.
diff --git a/test/functional/fixtures/autoload/provider/brokencall.vim b/test/functional/fixtures/autoload/provider/brokencall.vim
new file mode 100644
index 0000000000..2c83dd2b4a
--- /dev/null
+++ b/test/functional/fixtures/autoload/provider/brokencall.vim
@@ -0,0 +1,2 @@
+" A dummy test provider
+let g:provider#brokencall#enabled = 1
diff --git a/test/functional/fixtures/autoload/provider/brokenenabled.vim b/test/functional/fixtures/autoload/provider/brokenenabled.vim
new file mode 100644
index 0000000000..54ed11cedc
--- /dev/null
+++ b/test/functional/fixtures/autoload/provider/brokenenabled.vim
@@ -0,0 +1,6 @@
+" Dummy test provider, missing
+" let g:provider#brokenenabled#enabled = 0
+
+function! provider#brokenenabled#Call(method, args)
+  return 42
+endfunction
diff --git a/test/functional/fixtures/autoload/provider/clipboard.vim b/test/functional/fixtures/autoload/provider/clipboard.vim
index 6d777255c8..d1ddd81b12 100644
--- a/test/functional/fixtures/autoload/provider/clipboard.vim
+++ b/test/functional/fixtures/autoload/provider/clipboard.vim
@@ -35,6 +35,7 @@ function! s:methods.set(lines, regtype, reg)
   let g:test_clip[a:reg] = [a:lines, a:regtype]
 endfunction
 
+let provider#clipboard#enabled = 1
 
 function! provider#clipboard#Call(method, args)
   return call(s:methods[a:method],a:args,s:methods)
diff --git a/test/functional/provider/provider_spec.lua b/test/functional/provider/provider_spec.lua
new file mode 100644
index 0000000000..6f414f36f4
--- /dev/null
+++ b/test/functional/provider/provider_spec.lua
@@ -0,0 +1,19 @@
+
+local helpers = require('test.functional.helpers')(after_each)
+local clear, eq, feed_command, eval = helpers.clear, helpers.eq, helpers.feed_command, helpers.eval
+
+describe('Providers', function()
+  before_each(function()
+    clear('--cmd', 'let &rtp = "test/functional/fixtures,".&rtp')
+  end)
+
+  it('must set the enabled variable or fail', function()
+    eq(42, eval("provider#brokenenabled#Call('dosomething', [])"))
+	feed_command("call has('brokenenabled')")
+    eq(0, eval("has('brokenenabled')"))
+  end)
+
+  it('without Call() are enabled', function()
+    eq(1, eval("has('brokencall')"))
+  end)
+end)

From 66938b928c05b913f3a11e520d13ca854621799d Mon Sep 17 00:00:00 2001
From: "Justin M. Keyes" <justinkz@gmail.com>
Date: Sun, 4 Aug 2019 03:54:06 +0200
Subject: [PATCH 2/6] provider: decide status by g:loaded_xx_provider

---
 runtime/autoload/provider/clipboard.vim       | 22 +++++----
 runtime/autoload/provider/node.vim            |  9 ++--
 runtime/autoload/provider/python.vim          |  4 +-
 runtime/autoload/provider/python3.vim         |  4 +-
 runtime/autoload/provider/ruby.vim            |  8 ++--
 runtime/doc/develop.txt                       | 46 +++++++++----------
 src/nvim/eval.c                               | 36 +++++++++------
 .../fixtures/autoload/provider/brokencall.vim |  2 +-
 .../autoload/provider/brokenenabled.vim       |  4 +-
 .../fixtures/autoload/provider/clipboard.vim  |  4 +-
 test/functional/provider/provider_spec.lua    | 16 ++++---
 11 files changed, 78 insertions(+), 77 deletions(-)

diff --git a/runtime/autoload/provider/clipboard.vim b/runtime/autoload/provider/clipboard.vim
index e43f8fbb7a..9b79e5abec 100644
--- a/runtime/autoload/provider/clipboard.vim
+++ b/runtime/autoload/provider/clipboard.vim
@@ -1,6 +1,16 @@
 " The clipboard provider uses shell commands to communicate with the clipboard.
 " The provider function will only be registered if a supported command is
 " available.
+
+if exists('g:loaded_clipboard_provider')
+  finish
+endif
+" Default to FALSE.  Set by provider#clipboard#Executable() later.
+" To force a reload:
+"   :unlet g:loaded_clipboard_provider
+"   :runtime autoload/provider/clipboard.vim
+let g:loaded_clipboard_provider = 0
+
 let s:copy = {}
 let s:paste = {}
 let s:clipboard = {}
@@ -48,9 +58,6 @@ endfunction
 let s:cache_enabled = 1
 let s:err = ''
 
-" eval_has_provider checks the variable to verify provider status
-let g:provider#clipboard#enabled = 0
-
 function! provider#clipboard#Error() abort
   return s:err
 endfunction
@@ -123,12 +130,6 @@ function! provider#clipboard#Executable() abort
   return ''
 endfunction
 
-" Call this to setup/reload the provider
-function! provider#clipboard#Reload()
-  " #enabled is used by eval_has_provider()
-  let g:provider#clipboard#enabled = !empty(provider#clipboard#Executable())
-endfunction
-
 function! s:clipboard.get(reg) abort
   if type(s:paste[a:reg]) == v:t_func
     return s:paste[a:reg]()
@@ -195,4 +196,5 @@ function! provider#clipboard#Call(method, args) abort
   endtry
 endfunction
 
-call provider#clipboard#Reload()
+" eval_has_provider() decides based on this variable.
+let g:loaded_clipboard_provider = !empty(provider#clipboard#Executable())
diff --git a/runtime/autoload/provider/node.vim b/runtime/autoload/provider/node.vim
index 6413720605..dd2423fe2a 100644
--- a/runtime/autoload/provider/node.vim
+++ b/runtime/autoload/provider/node.vim
@@ -1,8 +1,7 @@
 if exists('g:loaded_node_provider')
   finish
 endif
-let g:loaded_node_provider = 1
-let g:provider#node#enabled = 0
+let g:loaded_node_provider = 0
 
 function! s:is_minimum_version(version, min_major, min_minor) abort
   if empty(a:version)
@@ -141,12 +140,10 @@ endfunction
 
 let s:err = ''
 let s:prog = provider#node#Detect()
+let g:loaded_node_provider = !empty(s:prog)
 
-if empty(s:prog)
+if !g:loaded_node_provider
   let s:err = 'Cannot find the "neovim" node package. Try :checkhealth'
-else
-  let g:provider#node#enabled = 1
 endif
 
 call remote#host#RegisterPlugin('node-provider', 'node', [])
-
diff --git a/runtime/autoload/provider/python.vim b/runtime/autoload/provider/python.vim
index d65506a55a..7921701141 100644
--- a/runtime/autoload/provider/python.vim
+++ b/runtime/autoload/provider/python.vim
@@ -7,10 +7,8 @@
 if exists('g:loaded_python_provider')
   finish
 endif
-let g:loaded_python_provider = 1
-
 let [s:prog, s:err] = provider#pythonx#Detect(2)
-let g:provider#python#enabled = !empty(s:prog)
+let g:loaded_python_provider = !empty(s:prog)
 
 function! provider#python#Prog() abort
   return s:prog
diff --git a/runtime/autoload/provider/python3.vim b/runtime/autoload/provider/python3.vim
index 469611c7ce..67350e3753 100644
--- a/runtime/autoload/provider/python3.vim
+++ b/runtime/autoload/provider/python3.vim
@@ -7,10 +7,8 @@
 if exists('g:loaded_python3_provider')
   finish
 endif
-let g:loaded_python3_provider = 1
-
 let [s:prog, s:err] = provider#pythonx#Detect(3)
-let g:provider#python3#enabled = !empty(s:prog)
+let g:loaded_python3_provider = !empty(s:prog)
 
 function! provider#python3#Prog() abort
   return s:prog
diff --git a/runtime/autoload/provider/ruby.vim b/runtime/autoload/provider/ruby.vim
index df43dffa40..f9d4f2b885 100644
--- a/runtime/autoload/provider/ruby.vim
+++ b/runtime/autoload/provider/ruby.vim
@@ -2,12 +2,11 @@
 if exists('g:loaded_ruby_provider')
   finish
 endif
-let g:loaded_ruby_provider = 1
+let g:loaded_ruby_provider = 0
 
 function! provider#ruby#Detect() abort
   return s:prog
 endfunction
-let g:provider#ruby#enabled = 0
 
 function! provider#ruby#Prog() abort
   return s:prog
@@ -63,11 +62,10 @@ endfunction
 let s:err = ''
 let s:prog = s:detect()
 let s:plugin_path = expand('<sfile>:p:h') . '/script_host.rb'
+let g:loaded_ruby_provider = !empty(s:prog)
 
-if empty(s:prog)
+if !g:loaded_ruby_provider
   let s:err = 'Cannot find the neovim RubyGem. Try :checkhealth'
-else
-  let g:provider#ruby#enabled = 1
 endif
 
 call remote#host#RegisterClone('legacy-ruby-provider', 'ruby')
diff --git a/runtime/doc/develop.txt b/runtime/doc/develop.txt
index 0f9e17e697..180612cf20 100644
--- a/runtime/doc/develop.txt
+++ b/runtime/doc/develop.txt
@@ -84,12 +84,11 @@ Developer guidelines				        *dev-guidelines*
 
 PROVIDERS 						*dev-provider*
 
-A goal of Nvim is to allow extension of the editor without special knowledge
-in the core. But some Vim components are too tightly coupled; in those cases
-a "provider" hook is exposed.
+A primary goal of Nvim is to allow extension of the editor without special
+knowledge in the core.  Some core functions are delegated to "providers"
+implemented as external scripts.
 
-Consider two examples of integration with external systems that are
-implemented in Vim and are now decoupled from Nvim core as providers:
+Examples:
 
 1. In the Vim source code, clipboard logic accounts for more than 1k lines of
    C source code (ui.c), to perform two tasks that are now accomplished with
@@ -101,29 +100,28 @@ implemented in Vim and are now decoupled from Nvim core as providers:
    scripting is performed by an external host process implemented in ~2k lines
    of Python.
 
-Ideally we could implement Python and clipboard integration in pure vimscript
-and without touching the C code. But this is infeasible without compromising
-backwards compatibility with Vim; that's where providers help.
+The provider framework invokes VimL from C.  It is composed of two functions
+in eval.c:
 
-The provider framework helps call vimscript from C. It is composed of two
-functions in eval.c:
-
-- eval_call_provider(name, method, arguments): calls provider#(name)#Call
+- eval_call_provider(name, method, arguments): calls provider#{name}#Call
   with the method and arguments.
-- eval_has_provider(name): Checks if a provider is implemented. Returns true
-  if the provider#(name)#enabled variable is not 0. Called by |has()|
-  (vimscript) to check if features are available.
-
-The provider#(name)#Call function implements integration with an external
-system, because shell commands and |RPC| clients are easier to work with in
-vimscript.
+- eval_has_provider(name): Checks the `g:loaded_{name}_provider` variable
+  which must be set by the provider script to indicate whether it is enabled
+  and working. Called by |has()| to check if features are available.
 
 For example, the Python provider is implemented by the
-autoload/provider/python.vim script; the variable provider#python#enabled is only
-1 if a valid external Python host is found. That works well with the
-`has('python')` expression (normally used by Python plugins) because if the
-Python host isn't installed then the plugin will "think" it is running in
-a Vim compiled without the "+python" feature.
+"autoload/provider/python.vim" script, which sets `g:loaded_python_provider`
+to TRUE only if a valid external Python host is found.  Then `has("python")`
+reflects whether Python support is working.
+
+							*provider-reload*
+Sometimes a GUI or other application may want to force a provider to
+"reload".  To reload a provider, undefine its "loaded" flag, then use
+|:runtime| to reload it: >
+
+    :unlet g:loaded_clipboard_provider
+    :runtime autoload/provider/clipboard.vim
+
 
 DOCUMENTATION						*dev-doc*
 
diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index ed01ca9f99..6b7a359508 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -23968,27 +23968,35 @@ typval_T eval_call_provider(char *provider, char *method, list_T *arguments)
   return rettv;
 }
 
-/// Check if a named provider is enabled
+/// Checks if a named provider is enabled.
 bool eval_has_provider(const char *provider)
 {
-  char enabled_varname[256];
-  int enabled_varname_len = snprintf(enabled_varname, sizeof(enabled_varname),
-                                     "provider#%s#enabled", provider);
-
+  char buf[256];
+  int len;
   typval_T tv;
-  if (get_var_tv(enabled_varname, enabled_varname_len, &tv,
-                 NULL, false, false) == FAIL) {
-    char call_varname[256];
-    snprintf(call_varname, sizeof(call_varname), "provider#%s#Call", provider);
-    int has_call = !!find_func((char_u *)call_varname);
 
-    if (has_call && p_lpl) {
-      emsgf("Provider '%s' failed to set %s", provider, enabled_varname);
+  // Get the g:loaded_xx_provider variable.
+  len = snprintf(buf, sizeof(buf), "g:loaded_%s_provider", provider);
+  if (get_var_tv(buf, len, &tv, NULL, false, true) == FAIL) {
+    // Trigger autoload once.
+    len = snprintf(buf, sizeof(buf), "provider#%s#bogus", provider);
+    script_autoload(buf, len, false);
+
+    // Retry the (non-autoload-style) variable.
+    len = snprintf(buf, sizeof(buf), "g:loaded_%s_provider", provider);
+    if (get_var_tv(buf, len, &tv, NULL, false, true) == FAIL) {
+      // Show a hint if Call() is defined but g:loaded_xx_provider is missing.
+      snprintf(buf, sizeof(buf), "provider#%s#Call", provider);
+      bool has_call = !!find_func((char_u *)buf);
+      if (has_call && p_lpl) {
+        emsgf("provider: %s: missing required variable g:loaded_%s_provider",
+              provider, provider);
+      }
+      return false;
     }
-    return false;
   }
 
-  return (tv.v_type == VAR_NUMBER) ? tv.vval.v_number != 0: true;
+  return (tv.v_type == VAR_NUMBER) ? !!tv.vval.v_number : false;
 }
 
 /// Writes "<sourcing_name>:<sourcing_lnum>" to `buf[bufsize]`.
diff --git a/test/functional/fixtures/autoload/provider/brokencall.vim b/test/functional/fixtures/autoload/provider/brokencall.vim
index 2c83dd2b4a..7dc5d828d2 100644
--- a/test/functional/fixtures/autoload/provider/brokencall.vim
+++ b/test/functional/fixtures/autoload/provider/brokencall.vim
@@ -1,2 +1,2 @@
 " A dummy test provider
-let g:provider#brokencall#enabled = 1
+let g:loaded_brokencall_provider = 1
diff --git a/test/functional/fixtures/autoload/provider/brokenenabled.vim b/test/functional/fixtures/autoload/provider/brokenenabled.vim
index 54ed11cedc..dd33ce66f3 100644
--- a/test/functional/fixtures/autoload/provider/brokenenabled.vim
+++ b/test/functional/fixtures/autoload/provider/brokenenabled.vim
@@ -1,5 +1,5 @@
-" Dummy test provider, missing
-" let g:provider#brokenenabled#enabled = 0
+" Dummy test provider, missing this required variable:
+"   let g:loaded_brokenenabled_provider = 0
 
 function! provider#brokenenabled#Call(method, args)
   return 42
diff --git a/test/functional/fixtures/autoload/provider/clipboard.vim b/test/functional/fixtures/autoload/provider/clipboard.vim
index d1ddd81b12..efa9f82bd4 100644
--- a/test/functional/fixtures/autoload/provider/clipboard.vim
+++ b/test/functional/fixtures/autoload/provider/clipboard.vim
@@ -1,3 +1,5 @@
+let g:loaded_clipboard_provider = 1
+
 let g:test_clip = { '+': [''], '*': [''], }
 
 let s:methods = {}
@@ -35,8 +37,6 @@ function! s:methods.set(lines, regtype, reg)
   let g:test_clip[a:reg] = [a:lines, a:regtype]
 endfunction
 
-let provider#clipboard#enabled = 1
-
 function! provider#clipboard#Call(method, args)
   return call(s:methods[a:method],a:args,s:methods)
 endfunction
diff --git a/test/functional/provider/provider_spec.lua b/test/functional/provider/provider_spec.lua
index 6f414f36f4..b690cf2566 100644
--- a/test/functional/provider/provider_spec.lua
+++ b/test/functional/provider/provider_spec.lua
@@ -1,19 +1,21 @@
 
 local helpers = require('test.functional.helpers')(after_each)
-local clear, eq, feed_command, eval = helpers.clear, helpers.eq, helpers.feed_command, helpers.eval
+local clear, eq, eval = helpers.clear, helpers.eq, helpers.eval
+local command = helpers.command
+local expect_err = helpers.expect_err
 
-describe('Providers', function()
+describe('providers', function()
   before_each(function()
     clear('--cmd', 'let &rtp = "test/functional/fixtures,".&rtp')
   end)
 
-  it('must set the enabled variable or fail', function()
-    eq(42, eval("provider#brokenenabled#Call('dosomething', [])"))
-	feed_command("call has('brokenenabled')")
-    eq(0, eval("has('brokenenabled')"))
+  it('must define g:loaded_xx_provider', function()
+    command('set loadplugins')
+    expect_err('Vim:provider: brokenenabled: missing required variable g:loaded_brokenenabled_provider',
+      eval, "has('brokenenabled')")
   end)
 
-  it('without Call() are enabled', function()
+  it('without Call() but with g:loaded_xx_provider', function()
     eq(1, eval("has('brokencall')"))
   end)
 end)

From 241956720d02d933b0b27097a3b0a1966f138d0b Mon Sep 17 00:00:00 2001
From: "Justin M. Keyes" <justinkz@gmail.com>
Date: Sun, 4 Aug 2019 12:06:24 +0200
Subject: [PATCH 3/6] provider: g:loaded_xx_provider=2 means "enabled and
 working"

Value of 1 cannot be used, because users might set that in their vimrc
to _disable_ a provider, which would confuse :checkhealth and has().
---
 runtime/autoload/provider/clipboard.vim                   | 6 +++---
 runtime/autoload/provider/node.vim                        | 6 +++---
 runtime/autoload/provider/python.vim                      | 2 +-
 runtime/autoload/provider/python3.vim                     | 2 +-
 runtime/autoload/provider/ruby.vim                        | 6 +++---
 runtime/doc/develop.txt                                   | 6 +++---
 runtime/doc/provider.txt                                  | 8 ++++----
 src/nvim/eval.c                                           | 4 +++-
 test/functional/fixtures/autoload/provider/brokencall.vim | 2 +-
 test/functional/fixtures/autoload/provider/clipboard.vim  | 2 +-
 10 files changed, 23 insertions(+), 21 deletions(-)

diff --git a/runtime/autoload/provider/clipboard.vim b/runtime/autoload/provider/clipboard.vim
index 9b79e5abec..ce140b0948 100644
--- a/runtime/autoload/provider/clipboard.vim
+++ b/runtime/autoload/provider/clipboard.vim
@@ -5,11 +5,11 @@
 if exists('g:loaded_clipboard_provider')
   finish
 endif
-" Default to FALSE.  Set by provider#clipboard#Executable() later.
+" Default to 1.  provider#clipboard#Executable() may set 2.
 " To force a reload:
 "   :unlet g:loaded_clipboard_provider
 "   :runtime autoload/provider/clipboard.vim
-let g:loaded_clipboard_provider = 0
+let g:loaded_clipboard_provider = 1
 
 let s:copy = {}
 let s:paste = {}
@@ -197,4 +197,4 @@ function! provider#clipboard#Call(method, args) abort
 endfunction
 
 " eval_has_provider() decides based on this variable.
-let g:loaded_clipboard_provider = !empty(provider#clipboard#Executable())
+let g:loaded_clipboard_provider = empty(provider#clipboard#Executable()) ? 1 : 2
diff --git a/runtime/autoload/provider/node.vim b/runtime/autoload/provider/node.vim
index dd2423fe2a..b2a3b3ee08 100644
--- a/runtime/autoload/provider/node.vim
+++ b/runtime/autoload/provider/node.vim
@@ -1,7 +1,7 @@
 if exists('g:loaded_node_provider')
   finish
 endif
-let g:loaded_node_provider = 0
+let g:loaded_node_provider = 1
 
 function! s:is_minimum_version(version, min_major, min_minor) abort
   if empty(a:version)
@@ -140,9 +140,9 @@ endfunction
 
 let s:err = ''
 let s:prog = provider#node#Detect()
-let g:loaded_node_provider = !empty(s:prog)
+let g:loaded_node_provider = empty(s:prog) ? 1 : 2
 
-if !g:loaded_node_provider
+if g:loaded_node_provider != 2
   let s:err = 'Cannot find the "neovim" node package. Try :checkhealth'
 endif
 
diff --git a/runtime/autoload/provider/python.vim b/runtime/autoload/provider/python.vim
index 7921701141..8a1d162784 100644
--- a/runtime/autoload/provider/python.vim
+++ b/runtime/autoload/provider/python.vim
@@ -8,7 +8,7 @@ if exists('g:loaded_python_provider')
   finish
 endif
 let [s:prog, s:err] = provider#pythonx#Detect(2)
-let g:loaded_python_provider = !empty(s:prog)
+let g:loaded_python_provider = empty(s:prog) ? 1 : 2
 
 function! provider#python#Prog() abort
   return s:prog
diff --git a/runtime/autoload/provider/python3.vim b/runtime/autoload/provider/python3.vim
index 67350e3753..38ef0cccfc 100644
--- a/runtime/autoload/provider/python3.vim
+++ b/runtime/autoload/provider/python3.vim
@@ -8,7 +8,7 @@ if exists('g:loaded_python3_provider')
   finish
 endif
 let [s:prog, s:err] = provider#pythonx#Detect(3)
-let g:loaded_python3_provider = !empty(s:prog)
+let g:loaded_python3_provider = empty(s:prog) ? 1 : 2
 
 function! provider#python3#Prog() abort
   return s:prog
diff --git a/runtime/autoload/provider/ruby.vim b/runtime/autoload/provider/ruby.vim
index f9d4f2b885..f843050df9 100644
--- a/runtime/autoload/provider/ruby.vim
+++ b/runtime/autoload/provider/ruby.vim
@@ -2,7 +2,7 @@
 if exists('g:loaded_ruby_provider')
   finish
 endif
-let g:loaded_ruby_provider = 0
+let g:loaded_ruby_provider = 1
 
 function! provider#ruby#Detect() abort
   return s:prog
@@ -62,9 +62,9 @@ endfunction
 let s:err = ''
 let s:prog = s:detect()
 let s:plugin_path = expand('<sfile>:p:h') . '/script_host.rb'
-let g:loaded_ruby_provider = !empty(s:prog)
+let g:loaded_ruby_provider = empty(s:prog) ? 1 : 2
 
-if !g:loaded_ruby_provider
+if g:loaded_ruby_provider != 2
   let s:err = 'Cannot find the neovim RubyGem. Try :checkhealth'
 endif
 
diff --git a/runtime/doc/develop.txt b/runtime/doc/develop.txt
index 180612cf20..3262d9dec7 100644
--- a/runtime/doc/develop.txt
+++ b/runtime/doc/develop.txt
@@ -106,12 +106,12 @@ in eval.c:
 - eval_call_provider(name, method, arguments): calls provider#{name}#Call
   with the method and arguments.
 - eval_has_provider(name): Checks the `g:loaded_{name}_provider` variable
-  which must be set by the provider script to indicate whether it is enabled
-  and working. Called by |has()| to check if features are available.
+  which must be set to 2 by the provider script to indicate that it is
+  "enabled and working". Called by |has()| to check if features are available.
 
 For example, the Python provider is implemented by the
 "autoload/provider/python.vim" script, which sets `g:loaded_python_provider`
-to TRUE only if a valid external Python host is found.  Then `has("python")`
+to 2 only if a valid external Python host is found.  Then `has("python")`
 reflects whether Python support is working.
 
 							*provider-reload*
diff --git a/runtime/doc/provider.txt b/runtime/doc/provider.txt
index 594c9602f4..dc045c360a 100644
--- a/runtime/doc/provider.txt
+++ b/runtime/doc/provider.txt
@@ -68,11 +68,11 @@ startup faster. Useful for working with virtualenvs.  >
 <
 						*g:loaded_python_provider*
 To disable Python 2 support: >
-    let g:loaded_python_provider = 1
+    let g:loaded_python_provider = 0
 <
 						*g:loaded_python3_provider*
 To disable Python 3 support: >
-    let g:loaded_python3_provider = 1
+    let g:loaded_python3_provider = 0
 
 
 PYTHON VIRTUALENVS ~
@@ -111,7 +111,7 @@ Run |:checkhealth| to see if your system is up-to-date.
 RUBY PROVIDER CONFIGURATION ~
 						*g:loaded_ruby_provider*
 To disable Ruby support: >
-    let g:loaded_ruby_provider = 1
+    let g:loaded_ruby_provider = 0
 <
 						*g:ruby_host_prog*
 Command to start the Ruby host. By default this is "neovim-ruby-host". With
@@ -142,7 +142,7 @@ Run |:checkhealth| to see if your system is up-to-date.
 NODEJS PROVIDER CONFIGURATION~
 						*g:loaded_node_provider*
 To disable Node.js support: >
-    :let g:loaded_node_provider = 1
+    :let g:loaded_node_provider = 0
 <
 						*g:node_host_prog*
 Command to start the Node.js host. Setting this makes startup faster.
diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index 6b7a359508..3bcec56b06 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -23996,7 +23996,9 @@ bool eval_has_provider(const char *provider)
     }
   }
 
-  return (tv.v_type == VAR_NUMBER) ? !!tv.vval.v_number : false;
+  return (tv.v_type == VAR_NUMBER)
+    ? 2 == tv.vval.v_number  // Value of 2 means "loaded and working".
+    : false;
 }
 
 /// Writes "<sourcing_name>:<sourcing_lnum>" to `buf[bufsize]`.
diff --git a/test/functional/fixtures/autoload/provider/brokencall.vim b/test/functional/fixtures/autoload/provider/brokencall.vim
index 7dc5d828d2..cad2b2a640 100644
--- a/test/functional/fixtures/autoload/provider/brokencall.vim
+++ b/test/functional/fixtures/autoload/provider/brokencall.vim
@@ -1,2 +1,2 @@
 " A dummy test provider
-let g:loaded_brokencall_provider = 1
+let g:loaded_brokencall_provider = 2
diff --git a/test/functional/fixtures/autoload/provider/clipboard.vim b/test/functional/fixtures/autoload/provider/clipboard.vim
index efa9f82bd4..41e486b745 100644
--- a/test/functional/fixtures/autoload/provider/clipboard.vim
+++ b/test/functional/fixtures/autoload/provider/clipboard.vim
@@ -1,4 +1,4 @@
-let g:loaded_clipboard_provider = 1
+let g:loaded_clipboard_provider = 2
 
 let g:test_clip = { '+': [''], '*': [''], }
 

From 5e6a08f2e6b21e83c9fb381042f0aed89de4598d Mon Sep 17 00:00:00 2001
From: "Justin M. Keyes" <justinkz@gmail.com>
Date: Sun, 4 Aug 2019 12:20:30 +0200
Subject: [PATCH 4/6] provider: skip non-provider has() feature-names

We don't want to retry autoload sourcing (slow) for every random has()
query that finds it way to eval_call_provider().
---
 src/nvim/eval.c                               | 21 +++++++++++++------
 .../fixtures/autoload/provider/brokencall.vim |  2 --
 .../{brokenenabled.vim => python.vim}         |  2 +-
 .../fixtures/autoload/provider/ruby.vim       |  2 ++
 test/functional/provider/provider_spec.lua    | 10 ++++++---
 5 files changed, 25 insertions(+), 12 deletions(-)
 delete mode 100644 test/functional/fixtures/autoload/provider/brokencall.vim
 rename test/functional/fixtures/autoload/provider/{brokenenabled.vim => python.vim} (70%)
 create mode 100644 test/functional/fixtures/autoload/provider/ruby.vim

diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index 3bcec56b06..dc18532b40 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -23969,28 +23969,37 @@ typval_T eval_call_provider(char *provider, char *method, list_T *arguments)
 }
 
 /// Checks if a named provider is enabled.
-bool eval_has_provider(const char *provider)
+bool eval_has_provider(const char *name)
 {
+  if (!strequal(name, "clipboard")
+      && !strequal(name, "python")
+      && !strequal(name, "python3")
+      && !strequal(name, "ruby")
+      && !strequal(name, "node")) {
+    // Avoid autoload for non-provider has() features.
+    return false;
+  }
+
   char buf[256];
   int len;
   typval_T tv;
 
   // Get the g:loaded_xx_provider variable.
-  len = snprintf(buf, sizeof(buf), "g:loaded_%s_provider", provider);
+  len = snprintf(buf, sizeof(buf), "g:loaded_%s_provider", name);
   if (get_var_tv(buf, len, &tv, NULL, false, true) == FAIL) {
     // Trigger autoload once.
-    len = snprintf(buf, sizeof(buf), "provider#%s#bogus", provider);
+    len = snprintf(buf, sizeof(buf), "provider#%s#bogus", name);
     script_autoload(buf, len, false);
 
     // Retry the (non-autoload-style) variable.
-    len = snprintf(buf, sizeof(buf), "g:loaded_%s_provider", provider);
+    len = snprintf(buf, sizeof(buf), "g:loaded_%s_provider", name);
     if (get_var_tv(buf, len, &tv, NULL, false, true) == FAIL) {
       // Show a hint if Call() is defined but g:loaded_xx_provider is missing.
-      snprintf(buf, sizeof(buf), "provider#%s#Call", provider);
+      snprintf(buf, sizeof(buf), "provider#%s#Call", name);
       bool has_call = !!find_func((char_u *)buf);
       if (has_call && p_lpl) {
         emsgf("provider: %s: missing required variable g:loaded_%s_provider",
-              provider, provider);
+              name, name);
       }
       return false;
     }
diff --git a/test/functional/fixtures/autoload/provider/brokencall.vim b/test/functional/fixtures/autoload/provider/brokencall.vim
deleted file mode 100644
index cad2b2a640..0000000000
--- a/test/functional/fixtures/autoload/provider/brokencall.vim
+++ /dev/null
@@ -1,2 +0,0 @@
-" A dummy test provider
-let g:loaded_brokencall_provider = 2
diff --git a/test/functional/fixtures/autoload/provider/brokenenabled.vim b/test/functional/fixtures/autoload/provider/python.vim
similarity index 70%
rename from test/functional/fixtures/autoload/provider/brokenenabled.vim
rename to test/functional/fixtures/autoload/provider/python.vim
index dd33ce66f3..d68360ac30 100644
--- a/test/functional/fixtures/autoload/provider/brokenenabled.vim
+++ b/test/functional/fixtures/autoload/provider/python.vim
@@ -1,6 +1,6 @@
 " Dummy test provider, missing this required variable:
 "   let g:loaded_brokenenabled_provider = 0
 
-function! provider#brokenenabled#Call(method, args)
+function! provider#python#Call(method, args)
   return 42
 endfunction
diff --git a/test/functional/fixtures/autoload/provider/ruby.vim b/test/functional/fixtures/autoload/provider/ruby.vim
new file mode 100644
index 0000000000..35becc27ff
--- /dev/null
+++ b/test/functional/fixtures/autoload/provider/ruby.vim
@@ -0,0 +1,2 @@
+" A dummy test provider
+let g:loaded_ruby_provider = 2
diff --git a/test/functional/provider/provider_spec.lua b/test/functional/provider/provider_spec.lua
index b690cf2566..4220ec21cf 100644
--- a/test/functional/provider/provider_spec.lua
+++ b/test/functional/provider/provider_spec.lua
@@ -11,11 +11,15 @@ describe('providers', function()
 
   it('must define g:loaded_xx_provider', function()
     command('set loadplugins')
-    expect_err('Vim:provider: brokenenabled: missing required variable g:loaded_brokenenabled_provider',
-      eval, "has('brokenenabled')")
+    -- Using test-fixture with broken impl:
+    -- test/functional/fixtures/autoload/provider/python.vim
+    expect_err('Vim:provider: python: missing required variable g:loaded_python_provider',
+      eval, "has('python')")
   end)
 
   it('without Call() but with g:loaded_xx_provider', function()
-    eq(1, eval("has('brokencall')"))
+    -- Using test-fixture with broken impl:
+    -- test/functional/fixtures/autoload/provider/ruby.vim
+    eq(1, eval("has('ruby')"))
   end)
 end)

From e952b7fc2f9838441308d1f71b98f108ae5faa8a Mon Sep 17 00:00:00 2001
From: "Justin M. Keyes" <justinkz@gmail.com>
Date: Sun, 4 Aug 2019 12:27:44 +0200
Subject: [PATCH 5/6] health.vim: check has("debug")

---
 runtime/autoload/health/nvim.vim | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/runtime/autoload/health/nvim.vim b/runtime/autoload/health/nvim.vim
index a2227e3b29..c25f5ee64f 100644
--- a/runtime/autoload/health/nvim.vim
+++ b/runtime/autoload/health/nvim.vim
@@ -123,7 +123,7 @@ function! s:check_performance() abort
   else
     call health#report_info(buildtype)
     call health#report_warn(
-          \ 'Non-optimized build-type. Nvim will be slower.',
+          \ 'Non-optimized '.(has('debug')?'(DEBUG) ':'').'build. Nvim will be slower.',
           \ ['Install a different Nvim package, or rebuild with `CMAKE_BUILD_TYPE=RelWithDebInfo`.',
           \  s:suggest_faq])
   endif

From 2141dc22625f73f3ce73460e581934b94f141cf9 Mon Sep 17 00:00:00 2001
From: "Justin M. Keyes" <justinkz@gmail.com>
Date: Sun, 4 Aug 2019 12:37:05 +0200
Subject: [PATCH 6/6] provider: check #Call() if g:loaded_xx_provider=2

---
 src/nvim/eval.c                            | 17 ++++++++++++++---
 test/functional/provider/provider_spec.lua |  9 +++++----
 2 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index dc18532b40..d82a081c27 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -23996,8 +23996,7 @@ bool eval_has_provider(const char *name)
     if (get_var_tv(buf, len, &tv, NULL, false, true) == FAIL) {
       // Show a hint if Call() is defined but g:loaded_xx_provider is missing.
       snprintf(buf, sizeof(buf), "provider#%s#Call", name);
-      bool has_call = !!find_func((char_u *)buf);
-      if (has_call && p_lpl) {
+      if (!!find_func((char_u *)buf) && p_lpl) {
         emsgf("provider: %s: missing required variable g:loaded_%s_provider",
               name, name);
       }
@@ -24005,9 +24004,21 @@ bool eval_has_provider(const char *name)
     }
   }
 
-  return (tv.v_type == VAR_NUMBER)
+  bool ok = (tv.v_type == VAR_NUMBER)
     ? 2 == tv.vval.v_number  // Value of 2 means "loaded and working".
     : false;
+
+  if (ok) {
+    // Call() must be defined if provider claims to be working.
+    snprintf(buf, sizeof(buf), "provider#%s#Call", name);
+    if (!find_func((char_u *)buf)) {
+      emsgf("provider: %s: g:loaded_%s_provider=2 but %s is not defined",
+            name, name, buf);
+      ok = false;
+    }
+  }
+
+  return ok;
 }
 
 /// Writes "<sourcing_name>:<sourcing_lnum>" to `buf[bufsize]`.
diff --git a/test/functional/provider/provider_spec.lua b/test/functional/provider/provider_spec.lua
index 4220ec21cf..bfb0bbc3a3 100644
--- a/test/functional/provider/provider_spec.lua
+++ b/test/functional/provider/provider_spec.lua
@@ -1,6 +1,6 @@
 
 local helpers = require('test.functional.helpers')(after_each)
-local clear, eq, eval = helpers.clear, helpers.eq, helpers.eval
+local clear, eval = helpers.clear, helpers.eval
 local command = helpers.command
 local expect_err = helpers.expect_err
 
@@ -9,7 +9,7 @@ describe('providers', function()
     clear('--cmd', 'let &rtp = "test/functional/fixtures,".&rtp')
   end)
 
-  it('must define g:loaded_xx_provider', function()
+  it('with #Call(), missing g:loaded_xx_provider', function()
     command('set loadplugins')
     -- Using test-fixture with broken impl:
     -- test/functional/fixtures/autoload/provider/python.vim
@@ -17,9 +17,10 @@ describe('providers', function()
       eval, "has('python')")
   end)
 
-  it('without Call() but with g:loaded_xx_provider', function()
+  it('with g:loaded_xx_provider, missing #Call()', function()
     -- Using test-fixture with broken impl:
     -- test/functional/fixtures/autoload/provider/ruby.vim
-    eq(1, eval("has('ruby')"))
+    expect_err('Vim:provider: ruby: g:loaded_ruby_provider=2 but provider#ruby#Call is not defined',
+      eval, "has('ruby')")
   end)
 end)