package manager: allow overriding deps with local cache

Author: dweiller

lib/compiler/build_runner.zig

@@ -373,6 +373,24 @@ pub fn main() !void {
     if (steps_menu)
         return steps(builder, stdout_writer);
 
+    inline for (dependencies.root_deps) |dep| {
+        if (!@hasDecl(dependencies.packages, dep[1])) continue;
+        const pkg = @field(dependencies.packages, dep[1]);
+        if (!@hasDecl(pkg, "local_override")) continue;
+        const allocator = single_threaded_arena.allocator();
+        const from = try std.process.getCwdAlloc(allocator);
+        const relative_path = try std.fs.path.relative(allocator, from, pkg.build_root);
+        if (pkg.local_override) {
+            if (builder.graph.system_package_mode) {
+                std.log.warn("ignoring local override of '{s}' in system mode, using '{s}'", .{
+                    dep[0], pkg.build_root,
+                });
+            } else {
+                std.log.warn("overriding dependency '{s}' with '{s}'", .{ dep[0], relative_path });
+            }
+        }
+    }
+
     var run: Run = .{
         .max_rss = max_rss,
         .max_rss_is_default = false,

src/Package/Fetch.zig

@@ -53,6 +53,7 @@ use_latest_commit: bool,
 /// This will either be relative to `global_cache`, or to the build root of
 /// the root package.
 package_root: Cache.Path,
+local_override: bool,
 error_bundle: ErrorBundle.Wip,
 manifest: ?Manifest,
 manifest_ast: std.zig.Ast,
@@ -97,6 +98,7 @@ pub const JobQueue = struct {
     thread_pool: *ThreadPool,
     wait_group: WaitGroup = .{},
     global_cache: Cache.Directory,
+    local_cache: ?Cache.Directory,
     /// If true then, no fetching occurs, and:
     /// * The `global_cache` directory is assumed to be the direct parent
     ///   directory of on-disk packages rather than having the "p/" directory
@@ -198,6 +200,11 @@ pub const JobQueue = struct {
                 }
             }
 
+            try buf.writer().print(
+                \\        pub const local_override = {};
+                \\
+            , .{fetch.local_override});
+
             try buf.writer().print(
                 \\        pub const build_root = "{q}";
                 \\
@@ -372,6 +379,35 @@ pub fn run(f: *Fetch) RunError!void {
         const prefixed_pkg_sub_path = "p" ++ s ++ expected_hash;
         const prefix_len: usize = if (f.job_queue.read_only) "p/".len else 0;
         const pkg_sub_path = prefixed_pkg_sub_path[prefix_len..];
+
+        if (f.job_queue.local_cache) |local_cache| local: {
+            const local_cache_path = if (f.job_queue.read_only) prefixed_pkg_sub_path else pkg_sub_path;
+            if (local_cache.handle.access(local_cache_path, .{})) |_| {
+                f.local_override = true;
+                if (f.job_queue.read_only) break :local;
+
+                assert(f.lazy_status != .unavailable);
+                f.package_root = .{
+                    .root_dir = local_cache,
+                    .sub_path = try arena.dupe(u8, local_cache_path),
+                };
+                try loadManifest(f, f.package_root);
+                try checkBuildFileExistence(f);
+                if (!f.job_queue.recursive) return;
+                return queueJobsForDeps(f);
+            } else |err| switch (err) {
+                error.FileNotFound => {},
+                else => |e| {
+                    try eb.addRootErrorMessage(.{
+                        .msg = try eb.printString("unable to open local package cache directory '{}{s}': {s}", .{
+                            local_cache, local_cache_path, @errorName(e),
+                        }),
+                    });
+                    return error.FetchFailed;
+                },
+            }
+        }
+
         if (cache_root.handle.access(pkg_sub_path, .{})) |_| {
             assert(f.lazy_status != .unavailable);
             f.package_root = .{
@@ -708,6 +744,7 @@ fn queueJobsForDeps(f: *Fetch) RunError!void {
                 .use_latest_commit = false,
 
                 .package_root = undefined,
+                .local_override = false,
                 .error_bundle = undefined,
                 .manifest = null,
                 .manifest_ast = undefined,
@@ -2279,6 +2316,7 @@ const TestFetchBuilder = struct {
             .allow_missing_paths_field = false,
 
             .package_root = undefined,
+            .local_override = false,
             .error_bundle = undefined,
             .manifest = null,
             .manifest_ast = undefined,

src/main.zig

@@ -5043,6 +5043,7 @@ fn cmdBuild(gpa: Allocator, arena: Allocator, args: []const []const u8) !void {
                     .http_client = &http_client,
                     .thread_pool = &thread_pool,
                     .global_cache = global_cache_directory,
+                    .local_cache = local_cache_directory,
                     .read_only = false,
                     .recursive = true,
                     .debug_hash = false,
@@ -5085,6 +5086,7 @@ fn cmdBuild(gpa: Allocator, arena: Allocator, args: []const []const u8) !void {
                     .use_latest_commit = false,
 
                     .package_root = undefined,
+                    .local_override = false,
                     .error_bundle = undefined,
                     .manifest = null,
                     .manifest_ast = undefined,
@@ -6902,6 +6904,7 @@ fn cmdFetch(
         .http_client = &http_client,
         .thread_pool = &thread_pool,
         .global_cache = global_cache_directory,
+        .local_cache = null,
         .recursive = false,
         .read_only = false,
         .debug_hash = debug_hash,
@@ -6925,6 +6928,7 @@ fn cmdFetch(
         .use_latest_commit = true,
 
         .package_root = undefined,
+        .local_override = false,
         .error_bundle = undefined,
         .manifest = null,
         .manifest_ast = undefined,