implements 'export' feature

compiler/astalgo.nim

@@ -585,8 +585,9 @@ proc StrTableContains(t: TStrTable, n: PSym): bool =
 proc StrTableRawInsert(data: var TSymSeq, n: PSym) = 
   var h: THash = n.name.h and high(data)
   while data[h] != nil: 
-    if data[h] == n: 
-      InternalError(n.info, "StrTableRawInsert: " & n.name.s)
+    if data[h] == n:
+      # allowed for 'export' feature:
+      #InternalError(n.info, "StrTableRawInsert: " & n.name.s)
       return
     h = nextTry(h, high(data))
   assert(data[h] == nil)
@@ -617,23 +618,23 @@ proc StrTableAdd(t: var TStrTable, n: PSym) =
   StrTableRawInsert(t.data, n)
   inc(t.counter)
 
-proc StrTableIncl*(t: var TStrTable, n: PSym): bool = 
+proc StrTableIncl*(t: var TStrTable, n: PSym): bool {.discardable.} =
   # returns true if n is already in the string table:
   # It is essential that `n` is written nevertheless!
   # This way the newest redefinition is picked by the semantic analyses!
   assert n.name != nil
   var h: THash = n.name.h and high(t.data)
-  while true: 
+  while true:
     var it = t.data[h]
-    if it == nil: break 
-    if it.name.id == n.name.id: 
+    if it == nil: break
+    if it.name.id == n.name.id:
       t.data[h] = n           # overwrite it with newer definition!
       return true             # found it
     h = nextTry(h, high(t.data))
-  if mustRehash(len(t.data), t.counter): 
+  if mustRehash(len(t.data), t.counter):
     StrTableEnlarge(t)
     StrTableRawInsert(t.data, n)
-  else: 
+  else:
     assert(t.data[h] == nil)
     t.data[h] = n
   inc(t.counter)

compiler/importer.nim

@@ -15,7 +15,6 @@ import
 
 proc evalImport*(c: PContext, n: PNode): PNode
 proc evalFrom*(c: PContext, n: PNode): PNode
-proc importAllSymbols*(c: PContext, fromMod: PSym)
 
 proc getModuleName*(n: PNode): string =
   # This returns a short relative module name without the nim extension
@@ -42,42 +41,43 @@ proc checkModuleName*(n: PNode): string =
   if result.len == 0:
     LocalError(n.info, errCannotOpenFile, modulename)
 
-proc rawImportSymbol(c: PContext, s: PSym) = 
+proc rawImportSymbol(c: PContext, s: PSym) =
   # This does not handle stubs, because otherwise loading on demand would be
   # pointless in practice. So importing stubs is fine here!
-  var copy = s # do not copy symbols when importing!
   # check if we have already a symbol of the same name:
   var check = StrTableGet(c.tab.stack[importTablePos], s.name)
-  if check != nil and check.id != copy.id: 
-    if s.kind notin OverloadableSyms: 
+  if check != nil and check.id != s.id:
+    if s.kind notin OverloadableSyms:
       # s and check need to be qualified:
-      Incl(c.AmbiguousSymbols, copy.id)
+      Incl(c.AmbiguousSymbols, s.id)
       Incl(c.AmbiguousSymbols, check.id)
-  StrTableAdd(c.tab.stack[importTablePos], copy)
-  if s.kind == skType: 
+  # thanks to 'export' feature, it could be we import the same symbol from
+  # multiple sources, so we need to call 'StrTableAdd' here:
+  StrTableAdd(c.tab.stack[importTablePos], s)
+  if s.kind == skType:
     var etyp = s.typ
-    if etyp.kind in {tyBool, tyEnum} and sfPure notin s.flags: 
-      for j in countup(0, sonsLen(etyp.n) - 1): 
+    if etyp.kind in {tyBool, tyEnum} and sfPure notin s.flags:
+      for j in countup(0, sonsLen(etyp.n) - 1):
         var e = etyp.n.sons[j].sym
-        if (e.Kind != skEnumField): 
+        if e.Kind != skEnumField: 
           InternalError(s.info, "rawImportSymbol") 
           # BUGFIX: because of aliases for enums the symbol may already
           # have been put into the symbol table
           # BUGFIX: but only iff they are the same symbols!
         var it: TIdentIter 
         check = InitIdentIter(it, c.tab.stack[importTablePos], e.name)
-        while check != nil: 
-          if check.id == e.id: 
+        while check != nil:
+          if check.id == e.id:
             e = nil
-            break 
+            break
           check = NextIdentIter(it, c.tab.stack[importTablePos])
-        if e != nil: 
+        if e != nil:
           rawImportSymbol(c, e)
   else:
     # rodgen assures that converters and patterns are no stubs
     if s.kind == skConverter: addConverter(c, s)
     if hasPattern(s): addPattern(c, s)
-  
+
 proc importSymbol(c: PContext, n: PNode, fromMod: PSym) = 
   let ident = lookups.considerAcc(n)
   let s = StrTableGet(fromMod.tab, ident)
@@ -98,17 +98,6 @@ proc importSymbol(c: PContext, n: PNode, fromMod: PSym) =
         rawImportSymbol(c, e)
         e = NextIdentIter(it, fromMod.tab)
     else: rawImportSymbol(c, s)
-  
-proc importAllSymbols(c: PContext, fromMod: PSym) = 
-  var i: TTabIter
-  var s = InitTabIter(i, fromMod.tab)
-  while s != nil: 
-    if s.kind != skModule: 
-      if s.kind != skEnumField: 
-        if s.Kind notin ExportableSymKinds:
-          InternalError(s.info, "importAllSymbols: " & $s.kind)
-        rawImportSymbol(c, s) # this is correct!
-    s = NextIter(i, fromMod.tab)
 
 proc importAllSymbolsExcept(c: PContext, fromMod: PSym, exceptSet: TIntSet) =
   var i: TTabIter
@@ -118,12 +107,34 @@ proc importAllSymbolsExcept(c: PContext, fromMod: PSym, exceptSet: TIntSet) =
       if s.kind != skEnumField:
         if s.Kind notin ExportableSymKinds:
           InternalError(s.info, "importAllSymbols: " & $s.kind)
-        if s.name.id notin exceptSet:
+        if exceptSet.empty or s.name.id notin exceptSet:
           rawImportSymbol(c, s)
     s = NextIter(i, fromMod.tab)
 
+proc importAllSymbols*(c: PContext, fromMod: PSym) =
+  var exceptSet: TIntSet
+  importAllSymbolsExcept(c, fromMod, exceptSet)
+
+proc importForwarded(c: PContext, n: PNode, exceptSet: TIntSet) =
+  if n.isNil: return
+  case n.kind
+  of nkExportStmt:
+    for a in n:
+      assert a.kind == nkSym
+      let s = a.sym
+      if s.kind == skModule:
+        importAllSymbolsExcept(c, s, exceptSet)
+      elif exceptSet.empty or s.name.id notin exceptSet:
+        rawImportSymbol(c, s)
+  of nkExportExceptStmt:
+    localError(n.info, errGenerated, "'export except' not implemented")
+  else:
+    for i in 0 ..safeLen(n)-1:
+      importForwarded(c, n.sons[i], exceptSet)
+
 proc evalImport(c: PContext, n: PNode): PNode = 
   result = n
+  var emptySet: TIntSet
   for i in countup(0, sonsLen(n) - 1): 
     var f = checkModuleName(n.sons[i])
     if f.len > 0:
@@ -132,7 +143,8 @@ proc evalImport(c: PContext, n: PNode): PNode =
         Message(n.sons[i].info, warnDeprecated, m.name.s) 
       # ``addDecl`` needs to be done before ``importAllSymbols``!
       addDecl(c, m)             # add symbol to symbol table of module
-      importAllSymbols(c, m)
+      importAllSymbolsExcept(c, m, emptySet)
+      importForwarded(c, m.ast, emptySet)
 
 proc evalFrom(c: PContext, n: PNode): PNode = 
   result = n
@@ -157,3 +169,4 @@ proc evalImportExcept*(c: PContext, n: PNode): PNode =
       let ident = lookups.considerAcc(n.sons[i])
       exceptSet.incl(ident.id)
     importAllSymbolsExcept(c, m, exceptSet)
+    importForwarded(c, m.ast, exceptSet)

compiler/semexprs.nim

@@ -1657,6 +1657,26 @@ proc fixImmediateParams(n: PNode): PNode =
   
   result = n
 
+proc semExport(c: PContext, n: PNode): PNode =
+  var x = newNodeI(n.kind, n.info)
+  #let L = if n.kind == nkExportExceptStmt: L = 1 else: n.len
+  for i in 0.. <n.len:
+    let a = n.sons[i]
+    var o: TOverloadIter
+    var s = initOverloadIter(o, c, a)
+    if s == nil:
+      localError(a.info, errGenerated, "invalid expr for 'export': " &
+          renderTree(a))
+    while s != nil:
+      if s.kind in ExportableSymKinds+{skModule}:
+        x.add(newSymNode(s, a.info))
+      s = nextOverloadIter(o, c, a)
+  if c.module.ast.isNil:
+    c.module.ast = newNodeI(nkStmtList, n.info)
+  assert c.module.ast.kind == nkStmtList
+  c.module.ast.add x
+  result = n
+
 proc semExpr(c: PContext, n: PNode, flags: TExprFlags = {}): PNode = 
   result = n
   if gCmd == cmdIdeTools: suggestExpr(c, n)
@@ -1859,6 +1879,9 @@ proc semExpr(c: PContext, n: PNode, flags: TExprFlags = {}): PNode =
   of nkIncludeStmt: 
     if not isTopLevel(c): LocalError(n.info, errXOnlyAtModuleScope, "include")
     result = evalInclude(c, n)
+  of nkExportStmt, nkExportExceptStmt:
+    if not isTopLevel(c): LocalError(n.info, errXOnlyAtModuleScope, "export")
+    result = semExport(c, n)
   of nkPragmaBlock:
     result = semPragmaBlock(c, n)
   of nkStaticStmt:

doc/manual.txt

@@ -3656,7 +3656,7 @@ don't need to instantiate the code multiple times, because types then can be
 manipulated using the unified internal symbol representation. In such context
 typedesc acts as any other type. You can create variables, store typedesc
 values inside containers and so on. For example, here is how we can create 
-a type-safe wrapper for the unsafe `printf` function form C:
+a type-safe wrapper for the unsafe `printf` function from C:
 
 .. code-block:: nimrod
   macro safePrintF(formatString: string{lit}, args: vararg[expr]): expr =
@@ -3744,7 +3744,7 @@ This is best illustrated by an example:
 Import statement
 ~~~~~~~~~~~~~~~~
 
-After the import statement a list of module names can follow or a single
+After the `import`:idx: statement a list of module names can follow or a single
 module name followed by an ``except`` to prevent some symbols to be imported:
 
 .. code-block:: nimrod
@@ -3754,6 +3754,33 @@ module name followed by an ``except`` to prevent some symbols to be imported:
   echo "$1" % "abc"
 
 
+Export statement
+~~~~~~~~~~~~~~~~
+
+An `export`:idx: statement can be used for symbol fowarding so that client
+modules don't need to import a module's dependencies:
+
+.. code-block:: nimrod
+  # module B
+  type TMyObject* = object
+
+.. code-block:: nimrod
+  # module A
+  import B
+  export B.TMyObject
+  
+  proc `$`*(x: TMyObject): string = "my object"
+
+
+.. code-block:: nimrod
+  # module C
+  import A
+  
+  # B.TMyObject has been imported implicitly here: 
+  var x: TMyObject
+  echo($x)
+
+
 Scope rules
 -----------
 Identifiers are valid from the point of their declaration until the end of

lib/pure/collections/intsets.nim

@@ -190,6 +190,11 @@ proc `$`*(s: TIntSet): string =
   ## The `$` operator for int sets.
   dollarImpl()
 
+proc empty*(s: TIntSet): bool {.inline.} =
+  ## returns true if `s` is empty. This is safe to call even before
+  ## the set has been initialized with `initIntSet`.
+  result = s.counter == 0
+
 when isMainModule:
   var x = initIntSet()
   x.incl(1)

tests/compile/mexporta.nim

@@ -0,0 +1,8 @@
+# module A
+import mexportb
+export mexportb.TMyObject, mexportb.xyz
+
+export mexportb.q
+
+proc `$`*(x: TMyObject): string = "my object"
+

tests/compile/mexportb.nim

@@ -0,0 +1,7 @@
+# module B
+type TMyObject* = object
+
+const xyz* = 13
+
+proc q*(x: int): int = 6
+proc q*(x: string): string = "8"

tests/compile/texport.nim

@@ -0,0 +1,10 @@
+discard """
+  output: "my object68"
+"""
+
+import mexporta
+
+# B.TMyObject has been imported implicitly here: 
+var x: TMyObject
+echo($x, q(0), q"0")
+

todo.txt

@@ -1,7 +1,7 @@
 version 0.9.2
 =============
 
-- 'export' feature
+- fix tfShared and tfNotNil
 - test&finish first class iterators:
   * nested iterators
   * test generic iterators

web/news.txt

@@ -51,6 +51,9 @@ Language Additions
   that ``nil`` is not allowed. However currently the compiler performs no
   advanced static checking for this; for now it's merely for documentation
   purposes.
+- An ``export`` statement has been added to the language: It can be used for
+  symbol forwarding so client modules don't have to import a module's 
+  dependencies explicitly.
 
 
 2012-09-23 Version 0.9.0 released