config: richer diagnostics for errors

Rather than storing a list of errors we now store a list of
"diagnostics." Each diagnostic has a richer set of structured
information, including a message, a key, the location where it occurred.

This lets us show more detailed messages, more human friendly messages, and
also let's us filter by key or location. We don't take advantage of
all of this capability in this initial commit, but we do use every field
for something.

src/config/theme.zig

@@ -4,7 +4,7 @@ const assert = std.debug.assert;
 const Allocator = std.mem.Allocator;
 const global_state = &@import("../global.zig").state;
 const internal_os = @import("../os/main.zig");
-const ErrorList = @import("ErrorList.zig");
+const cli = @import("../cli.zig");
 
 /// Location of possible themes. The order of this enum matters because it
 /// defines the priority of theme search (from top to bottom).
@@ -107,19 +107,19 @@ pub const LocationIterator = struct {
 pub fn open(
     arena_alloc: Allocator,
     theme: []const u8,
-    errors: *ErrorList,
+    diags: *cli.DiagnosticList,
 ) error{OutOfMemory}!?std.fs.File {
 
     // Absolute themes are loaded a different path.
     if (std.fs.path.isAbsolute(theme)) return try openAbsolute(
         arena_alloc,
         theme,
-        errors,
+        diags,
     );
 
     const basename = std.fs.path.basename(theme);
     if (!std.mem.eql(u8, theme, basename)) {
-        try errors.add(arena_alloc, .{
+        try diags.append(arena_alloc, .{
             .message = try std.fmt.allocPrintZ(
                 arena_alloc,
                 "theme \"{s}\" cannot include path separators unless it is an absolute path",
@@ -143,7 +143,7 @@ pub fn open(
 
             // Anything else is an error we log and give up on.
             else => {
-                try errors.add(arena_alloc, .{
+                try diags.append(arena_alloc, .{
                     .message = try std.fmt.allocPrintZ(
                         arena_alloc,
                         "failed to load theme \"{s}\" from the file \"{s}\": {}",
@@ -163,7 +163,7 @@ pub fn open(
     it.reset();
     while (try it.next()) |loc| {
         const path = try std.fs.path.join(arena_alloc, &.{ loc.dir, theme });
-        try errors.add(arena_alloc, .{
+        try diags.append(arena_alloc, .{
             .message = try std.fmt.allocPrintZ(
                 arena_alloc,
                 "theme \"{s}\" not found, tried path \"{s}\"",
@@ -186,18 +186,18 @@ pub fn open(
 pub fn openAbsolute(
     arena_alloc: Allocator,
     theme: []const u8,
-    errors: *ErrorList,
+    diags: *cli.DiagnosticList,
 ) error{OutOfMemory}!?std.fs.File {
     return std.fs.openFileAbsolute(theme, .{}) catch |err| {
         switch (err) {
-            error.FileNotFound => try errors.add(arena_alloc, .{
+            error.FileNotFound => try diags.append(arena_alloc, .{
                 .message = try std.fmt.allocPrintZ(
                     arena_alloc,
                     "failed to load theme from the path \"{s}\"",
                     .{theme},
                 ),
             }),
-            else => try errors.add(arena_alloc, .{
+            else => try diags.append(arena_alloc, .{
                 .message = try std.fmt.allocPrintZ(
                     arena_alloc,
                     "failed to load theme from the path \"{s}\": {}",