Support for user-configurable build options

src/BuildAssociatedConfig.zig

@@ -1,4 +1,44 @@
-// Configuration options related to a specific `BuildFile`.
+//! Configuration options related to a specific `BuildFile`.
+const std = @import("std");
+
+pub const BuildOption = struct {
+    name: []const u8,
+    value: ?[]const u8 = null,
+
+    /// Frees the strings assocated with this `BuildOption` and invalidates `self`.
+    pub fn deinit(self: *BuildOption, allocator: std.mem.Allocator) void {
+        allocator.free(self.name);
+        if (self.value) |val| {
+            allocator.free(val);
+        }
+        self.* = undefined;
+    }
+
+    /// Duplicates the `BuildOption`, copying internal strings. Caller owns returned option with contents
+    /// allocated using `allocator`.
+    pub fn dupe(self: BuildOption, allocator: std.mem.Allocator) !BuildOption {
+        const copy_name = try allocator.dupe(u8, self.name);
+        errdefer allocator.free(copy_name);
+        const copy_value = if (self.value) |val|
+            try allocator.dupe(u8, val)
+        else
+            null;
+        return BuildOption{
+            .name = copy_name,
+            .value = copy_value,
+        };
+    }
+
+    /// Formats the `BuildOption` as a command line parameter compatible with `zig build`. This will either be
+    /// `-Dname=value` or `-Dname`. Caller owns returned slice allocated using `allocator`.
+    pub fn formatParam(self: BuildOption, allocator: std.mem.Allocator) ![]const u8 {
+        if (self.value) |val| {
+            return try std.fmt.allocPrint(allocator, "-D{s}={s}", .{ self.name, val });
+        } else {
+            return try std.fmt.allocPrint(allocator, "-D{s}", .{self.name});
+        }
+    }
+};
 
 /// If provided this path is used when resolving `@import("builtin")`
 /// It is relative to the directory containing the `build.zig`
@@ -6,3 +46,6 @@
 /// This file should contain the output of:
 /// `zig build-exe/build-lib/build-obj --show-builtin <options>`
 relative_builtin_path: ?[]const u8 = null,
+
+/// If provided, this list of options will be passed to `build.zig`.
+build_options: ?[]BuildOption = null,

src/DocumentStore.zig

@@ -23,9 +23,16 @@ const BuildFile = struct {
     uri: []const u8,
     config: BuildFileConfig,
     builtin_uri: ?[]const u8 = null,
+    build_options: ?[]BuildAssociatedConfig.BuildOption = null,
 
     pub fn destroy(self: *BuildFile, allocator: std.mem.Allocator) void {
         if (self.builtin_uri) |builtin_uri| allocator.free(builtin_uri);
+        if (self.build_options) |opts| {
+            for (opts) |*opt| {
+                opt.deinit(allocator);
+            }
+            allocator.free(opts);
+        }
         allocator.destroy(self);
     }
 };
@@ -115,6 +122,8 @@ fn loadBuildAssociatedConfiguration(allocator: std.mem.Allocator, build_file: *B
         const config_file_path = try std.fs.path.join(allocator, &[_][]const u8{ directory_path, "zls.build.json" });
         defer allocator.free(config_file_path);
 
+        log.info("Attempting to load build-associated config from {s}", .{config_file_path});
+
         var config_file = std.fs.cwd().openFile(config_file_path, .{}) catch |err| {
             if (err == error.FileNotFound) return;
             return err;
@@ -133,6 +142,21 @@ fn loadBuildAssociatedConfiguration(allocator: std.mem.Allocator, build_file: *B
         defer allocator.free(absolute_builtin_path);
         build_file.builtin_uri = try URI.fromPath(allocator, absolute_builtin_path);
     }
+
+    if (build_associated_config.build_options) |opts| {
+        // Copy options out of json parse result since they will be invalidated
+        var build_opts = try std.ArrayListUnmanaged(BuildAssociatedConfig.BuildOption).initCapacity(allocator, opts.len);
+        errdefer {
+            for (build_opts.items) |*opt| {
+                opt.deinit(allocator);
+            }
+            build_opts.deinit(allocator);
+        }
+        for (opts) |opt| {
+            try build_opts.append(allocator, try opt.dupe(allocator));
+        }
+        build_file.build_options = build_opts.toOwnedSlice(allocator);
+    }
 }
 
 const LoadBuildConfigContext = struct {
@@ -156,26 +180,45 @@ fn loadBuildConfiguration(context: LoadBuildConfigContext) !void {
     const global_cache_path = context.global_cache_path;
     const zig_exe_path = context.zig_exe_path;
 
+    var arena = std.heap.ArenaAllocator.init(allocator);
+    defer arena.deinit();
+    const arena_allocator = arena.allocator();
+
     const build_file_path = context.build_file_path orelse try URI.parse(allocator, build_file.uri);
     defer if (context.build_file_path == null) allocator.free(build_file_path);
     const directory_path = build_file_path[0 .. build_file_path.len - "build.zig".len];
 
-    const args: []const []const u8 = &[_][]const u8{
-        zig_exe_path,
-        "run",
-        build_runner_path,
-        "--cache-dir",
-        global_cache_path,
-        "--pkg-begin",
-        "@build@",
-        build_file_path,
-        "--pkg-end",
-        "--",
-        zig_exe_path,
-        directory_path,
-        context.cache_root,
-        context.global_cache_root,
-    };
+    // enough capacity for arguments always passed to the build runner plus a couple build options
+    var arglist = try std.ArrayListUnmanaged([]const u8).initCapacity(arena_allocator, 32);
+    defer arglist.deinit(arena_allocator);
+
+    try arglist.appendSlice(
+        arena_allocator,
+        &[_][]const u8{
+            zig_exe_path,
+            "run",
+            build_runner_path,
+            "--cache-dir",
+            global_cache_path,
+            "--pkg-begin",
+            "@build@",
+            build_file_path,
+            "--pkg-end",
+            "--",
+            zig_exe_path,
+            directory_path,
+            context.cache_root,
+            context.global_cache_root,
+        },
+    );
+
+    if (build_file.build_options) |opts| {
+        for (opts) |opt| {
+            try arglist.append(allocator, try opt.formatParam(arena_allocator));
+        }
+    }
+
+    const args: []const []const u8 = arglist.items;
 
     const zig_run_result = try std.ChildProcess.exec(.{
         .allocator = allocator,

src/special/build_runner.zig

@@ -57,6 +57,30 @@ pub fn main() !void {
 
     defer builder.destroy();
 
+    while (nextArg(args, &arg_idx)) |arg| {
+        if (std.mem.startsWith(u8, arg, "-D")) {
+            const option_contents = arg[2..];
+            if (option_contents.len == 0) {
+                log.err("Expected option name after '-D'\n\n", .{});
+                return error.InvalidArgs;
+            }
+            if (std.mem.indexOfScalar(u8, option_contents, '=')) |name_end| {
+                const option_name = option_contents[0..name_end];
+                const option_value = option_contents[name_end + 1 ..];
+                if (try builder.addUserInputOption(option_name, option_value)) {
+                    log.err("Option conflict '-D{s}'\n\n", .{option_name});
+                    return error.InvalidArgs;
+                }
+            } else {
+                const option_name = option_contents;
+                if (try builder.addUserInputFlag(option_name)) {
+                    log.err("Option conflict '-D{s}'\n\n", .{option_name});
+                    return error.InvalidArgs;
+                }
+            }
+        }
+    }
+
     builder.resolveInstallPrefix(null, Builder.DirList{});
     try runBuild(builder);