bundler: Add --ignore-dce-annotations, and other DCE annotation rel…

…ated stuff (#12808) Co-authored-by: paperdave <[email protected]> Co-authored-by: Jarred Sumner <[email protected]>
oven-sh · Aug 1, 2024 · c2cf528 · c2cf528
1 parent 9911407
commit c2cf528
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Showing 14 changed files with 286 additions and 166 deletions.
diff --git a/docs/bundler/vs-esbuild.md b/docs/bundler/vs-esbuild.md
@@ -208,8 +208,7 @@ In Bun's CLI, simple boolean flags like `--minify` do not accept an argument. Ot
 ---
 
 - `--ignore-annotations`
-- n/a
-- Not supported
+- `--ignore-dce-annotations`
 
 ---
 

diff --git a/src/api/schema.zig b/src/api/schema.zig
@@ -1687,6 +1687,9 @@ pub const Api = struct {
         /// packages
         packages: ?PackagesMode = null,
 
+        /// ignore_dce_annotations
+        ignore_dce_annotations: bool,
+
         pub fn decode(reader: anytype) anyerror!TransformOptions {
             var this = std.mem.zeroes(TransformOptions);
 

diff --git a/src/bun_js.zig b/src/bun_js.zig
@@ -88,6 +88,7 @@ pub const Run = struct {
 
         b.options.minify_identifiers = ctx.bundler_options.minify_identifiers;
         b.options.minify_whitespace = ctx.bundler_options.minify_whitespace;
+        b.options.ignore_dce_annotations = ctx.bundler_options.ignore_dce_annotations;
         b.resolver.opts.minify_identifiers = ctx.bundler_options.minify_identifiers;
         b.resolver.opts.minify_whitespace = ctx.bundler_options.minify_whitespace;
 
@@ -232,6 +233,7 @@ pub const Run = struct {
 
         b.options.minify_identifiers = ctx.bundler_options.minify_identifiers;
         b.options.minify_whitespace = ctx.bundler_options.minify_whitespace;
+        b.options.ignore_dce_annotations = ctx.bundler_options.ignore_dce_annotations;
         b.resolver.opts.minify_identifiers = ctx.bundler_options.minify_identifiers;
         b.resolver.opts.minify_whitespace = ctx.bundler_options.minify_whitespace;
 

diff --git a/src/bundler.zig b/src/bundler.zig
@@ -1144,6 +1144,7 @@ pub const Bundler = struct {
                     .minify_identifiers = bundler.options.minify_identifiers,
                     .transform_only = bundler.options.transform_only,
                     .runtime_transpiler_cache = runtime_transpiler_cache,
+                    .print_dce_annotations = bundler.options.emit_dce_annotations,
                 },
                 enable_source_map,
             ),
@@ -1167,6 +1168,7 @@ pub const Bundler = struct {
                     .transform_only = bundler.options.transform_only,
                     .import_meta_ref = ast.import_meta_ref,
                     .runtime_transpiler_cache = runtime_transpiler_cache,
+                    .print_dce_annotations = bundler.options.emit_dce_annotations,
                 },
                 enable_source_map,
             ),
@@ -1199,6 +1201,7 @@ pub const Bundler = struct {
                         .inline_require_and_import_errors = false,
                         .import_meta_ref = ast.import_meta_ref,
                         .runtime_transpiler_cache = runtime_transpiler_cache,
+                        .print_dce_annotations = bundler.options.emit_dce_annotations,
                     },
                     enable_source_map,
                 ),
@@ -1405,6 +1408,8 @@ pub const Bundler = struct {
                 opts.features.runtime_transpiler_cache = this_parse.runtime_transpiler_cache;
                 opts.transform_only = bundler.options.transform_only;
 
+                opts.ignore_dce_annotations = bundler.options.ignore_dce_annotations;
+
                 // @bun annotation
                 opts.features.dont_bundle_twice = this_parse.dont_bundle_twice;
 

diff --git a/src/bundler/bundle_v2.zig b/src/bundler/bundle_v2.zig
@@ -760,6 +760,9 @@ pub const BundleV2 = struct {
         generator.linker.options.minify_syntax = bundler.options.minify_syntax;
         generator.linker.options.minify_identifiers = bundler.options.minify_identifiers;
         generator.linker.options.minify_whitespace = bundler.options.minify_whitespace;
+        generator.linker.options.emit_dce_annotations = bundler.options.emit_dce_annotations;
+        generator.linker.options.ignore_dce_annotations = bundler.options.ignore_dce_annotations;
+
         generator.linker.options.source_maps = bundler.options.source_map;
         generator.linker.options.tree_shaking = bundler.options.tree_shaking;
         generator.linker.options.public_path = bundler.options.public_path;
@@ -1627,6 +1630,7 @@ pub const BundleV2 = struct {
                 .extension_order = &.{},
                 .env_files = &.{},
                 .conditions = config.conditions.map.keys(),
+                .ignore_dce_annotations = bundler.options.ignore_dce_annotations,
             },
             completion.env,
         );
@@ -2874,6 +2878,7 @@ pub const ParseTask = struct {
         opts.features.minify_syntax = bundler.options.minify_syntax;
         opts.features.minify_identifiers = bundler.options.minify_identifiers;
         opts.features.emit_decorator_metadata = bundler.options.emit_decorator_metadata;
+        opts.ignore_dce_annotations = bundler.options.ignore_dce_annotations and !source.index.isRuntime();
 
         opts.tree_shaking = if (source.index.isRuntime()) true else bundler.options.tree_shaking;
         opts.module_type = task.module_type;
@@ -3851,6 +3856,7 @@ pub const LinkerContext = struct {
     pub const LinkerOptions = struct {
         output_format: options.OutputFormat = .esm,
         ignore_dce_annotations: bool = false,
+        emit_dce_annotations: bool = true,
         tree_shaking: bool = true,
         minify_whitespace: bool = false,
         minify_syntax: bool = false,
@@ -6804,6 +6810,7 @@ pub const LinkerContext = struct {
                 .minify_whitespace = c.options.minify_whitespace,
                 .minify_identifiers = c.options.minify_identifiers,
                 .minify_syntax = c.options.minify_syntax,
+                .print_dce_annotations = c.options.emit_dce_annotations,
                 // .const_values = c.graph.const_values,
             };
 
@@ -7714,6 +7721,7 @@ pub const LinkerContext = struct {
             .require_or_import_meta_for_source_callback = js_printer.RequireOrImportMeta.Callback.init(LinkerContext, requireOrImportMetaForSource, c),
 
             .minify_whitespace = c.options.minify_whitespace,
+            .print_dce_annotations = c.options.emit_dce_annotations,
             .minify_syntax = c.options.minify_syntax,
             // .const_values = c.graph.const_values,
         };
@@ -9015,6 +9023,7 @@ pub const LinkerContext = struct {
             .minify_whitespace = c.options.minify_whitespace,
             .minify_syntax = c.options.minify_syntax,
             .module_type = c.options.output_format,
+            .print_dce_annotations = c.options.emit_dce_annotations,
             .has_run_symbol_renamer = true,
 
             .allocator = allocator,

diff --git a/src/cli.zig b/src/cli.zig
@@ -185,6 +185,7 @@ pub const Arguments = struct {
         clap.parseParam("--jsx-fragment <STR>              Changes the function called when compiling JSX fragments") catch unreachable,
         clap.parseParam("--jsx-import-source <STR>         Declares the module specifier to be used for importing the jsx and jsxs factory functions. Default: \"react\"") catch unreachable,
         clap.parseParam("--jsx-runtime <STR>               \"automatic\" (default) or \"classic\"") catch unreachable,
+        clap.parseParam("--ignore-dce-annotations          Ignore tree-shaking annotations such as @__PURE__") catch unreachable,
     };
     const runtime_params_ = [_]ParamType{
         clap.parseParam("--watch                           Automatically restart the process on file change") catch unreachable,
@@ -238,7 +239,7 @@ pub const Arguments = struct {
         clap.parseParam("--no-clear-screen                Disable clearing the terminal screen on reload when --watch is enabled") catch unreachable,
         clap.parseParam("--target <STR>                   The intended execution environment for the bundle. \"browser\", \"bun\" or \"node\"") catch unreachable,
         clap.parseParam("--outdir <STR>                   Default to \"dist\" if multiple files") catch unreachable,
-        clap.parseParam("--outfile <STR>                   Write to a file") catch unreachable,
+        clap.parseParam("--outfile <STR>                  Write to a file") catch unreachable,
         clap.parseParam("--sourcemap <STR>?               Build with sourcemaps - 'inline', 'external', or 'none'") catch unreachable,
         clap.parseParam("--format <STR>                   Specifies the module format to build to. Only \"esm\" is supported.") catch unreachable,
         clap.parseParam("--root <STR>                     Root directory used for multiple entry points") catch unreachable,
@@ -251,10 +252,11 @@ pub const Arguments = struct {
         clap.parseParam("--asset-naming <STR>             Customize asset filenames. Defaults to \"[name]-[hash].[ext]\"") catch unreachable,
         clap.parseParam("--server-components              Enable React Server Components (experimental)") catch unreachable,
         clap.parseParam("--no-bundle                      Transpile file only, do not bundle") catch unreachable,
+        clap.parseParam("--emit-dce-annotations           Re-emit DCE annotations in bundles. Enabled by default unless --minify-whitespace is passed.") catch unreachable,
         clap.parseParam("--minify                         Enable all minification flags") catch unreachable,
         clap.parseParam("--minify-syntax                  Minify syntax and inline data") catch unreachable,
         clap.parseParam("--minify-whitespace              Minify whitespace") catch unreachable,
-        clap.parseParam("--minify-identifiers              Minify identifiers") catch unreachable,
+        clap.parseParam("--minify-identifiers             Minify identifiers") catch unreachable,
         clap.parseParam("--dump-environment-variables") catch unreachable,
         clap.parseParam("--conditions <STR>...            Pass custom conditions to resolve") catch unreachable,
     };
@@ -697,6 +699,8 @@ pub const Arguments = struct {
         const output_dir: ?string = null;
         const output_file: ?string = null;
 
+        ctx.bundler_options.ignore_dce_annotations = args.flag("--ignore-dce-annotations");
+
         if (cmd == .BuildCommand) {
             ctx.bundler_options.transform_only = args.flag("--no-bundle");
 
@@ -709,6 +713,9 @@ pub const Arguments = struct {
             ctx.bundler_options.minify_whitespace = minify_flag or args.flag("--minify-whitespace");
             ctx.bundler_options.minify_identifiers = minify_flag or args.flag("--minify-identifiers");
 
+            ctx.bundler_options.emit_dce_annotations = args.flag("--emit-dce-annotations") or
+                !ctx.bundler_options.minify_whitespace;
+
             if (args.options("--external").len > 0) {
                 var externals = try allocator.alloc([]u8, args.options("--external").len);
                 for (args.options("--external"), 0..) |external, i| {
@@ -1275,6 +1282,8 @@ pub const Command = struct {
             minify_syntax: bool = false,
             minify_whitespace: bool = false,
             minify_identifiers: bool = false,
+            ignore_dce_annotations: bool = false,
+            emit_dce_annotations: bool = true,
         };
 
         pub fn create(allocator: std.mem.Allocator, log: *logger.Log, comptime command: Command.Tag) anyerror!Context {

diff --git a/src/cli/build_command.zig b/src/cli/build_command.zig
@@ -114,6 +114,12 @@ pub const BuildCommand = struct {
         this_bundler.options.minify_identifiers = ctx.bundler_options.minify_identifiers;
         this_bundler.resolver.opts.minify_identifiers = ctx.bundler_options.minify_identifiers;
 
+        this_bundler.options.emit_dce_annotations = ctx.bundler_options.emit_dce_annotations;
+        this_bundler.resolver.opts.emit_dce_annotations = ctx.bundler_options.emit_dce_annotations;
+
+        this_bundler.options.ignore_dce_annotations = ctx.bundler_options.ignore_dce_annotations;
+        this_bundler.resolver.opts.ignore_dce_annotations = ctx.bundler_options.ignore_dce_annotations;
+
         if (ctx.bundler_options.compile) {
             if (ctx.bundler_options.code_splitting) {
                 Output.prettyErrorln("<r><red>error<r><d>:<r> cannot use --compile with --splitting", .{});

diff --git a/src/js_parser.zig b/src/js_parser.zig
@@ -1935,13 +1935,14 @@ pub const SideEffects = enum(u1) {
                 }
             },
 
-            .e_call => |call| {
-
+            inline .e_call, .e_new => |call| {
                 // A call that has been marked "__PURE__" can be removed if all arguments
                 // can be removed. The annotation causes us to ignore the target.
                 if (call.can_be_unwrapped_if_unused) {
                     if (call.args.len > 0) {
                         return Expr.joinAllWithCommaCallback(call.args.slice(), @TypeOf(p), p, comptime simplifyUnusedExpr, p.allocator);
+                    } else {
+                        return Expr.empty;
                     }
                 }
             },
@@ -2071,23 +2072,6 @@ pub const SideEffects = enum(u1) {
                 );
             },
 
-            .e_new => |call| {
-                // A constructor call that has been marked "__PURE__" can be removed if all arguments
-                // can be removed. The annotation causes us to ignore the target.
-                if (call.can_be_unwrapped_if_unused) {
-                    if (call.args.len > 0) {
-                        return Expr.joinAllWithCommaCallback(
-                            call.args.slice(),
-                            @TypeOf(p),
-                            p,
-                            comptime simplifyUnusedExpr,
-                            p.allocator,
-                        );
-                    }
-
-                    return null;
-                }
-            },
             else => {},
         }
 
@@ -3122,6 +3106,10 @@ pub const Parser = struct {
                 hasher.update("NO_TS");
             }
 
+            if (this.ignore_dce_annotations) {
+                hasher.update("no_dce");
+            }
+
             this.features.hashForRuntimeTranspiler(hasher);
         }
 
@@ -13201,12 +13189,6 @@ fn NewParser_(
                     .e_new => |ex| {
                         ex.can_be_unwrapped_if_unused = true;
                     },
-
-                    // this is specifically added only to support our implementation
-                    // of '__require' for --target=node, for /* @__PURE__ */ import.meta.url
-                    .e_dot => |ex| {
-                        ex.can_be_removed_if_unused = true;
-                    },
                     else => {},
                 }
             }
@@ -20860,7 +20842,13 @@ fn NewParser_(
                 E.Call{
                     .target = target,
                     .args = ExprNodeList.init(args_list),
-                    .can_be_unwrapped_if_unused = all_values_are_pure,
+                    // TODO: make these fully tree-shakable. this annotation
+                    // as-is is incorrect.  This would be done by changing all
+                    // enum wrappers into `var Enum = ...` instead of two
+                    // separate statements. This way, the @__PURE__ annotation
+                    // is attached to the variable binding.
+                    //
+                    // .can_be_unwrapped_if_unused = all_values_are_pure,
                 },
                 stmt_loc,
             );

diff --git a/src/js_printer.zig b/src/js_printer.zig
@@ -65,8 +65,8 @@ const ascii_only_always_on_unless_minifying = true;
 fn formatUnsignedIntegerBetween(comptime len: u16, buf: *[len]u8, val: u64) void {
     comptime var i: u16 = len;
     var remainder = val;
-    // Write out the number from the end to the front
 
+    // Write out the number from the end to the front
     inline while (i > 0) {
         comptime i -= 1;
         buf[comptime i] = @as(u8, @intCast((remainder % 10))) + '0';
@@ -536,6 +536,8 @@ pub const Options = struct {
     minify_whitespace: bool = false,
     minify_identifiers: bool = false,
     minify_syntax: bool = false,
+    print_dce_annotations: bool = true,
+
     transform_only: bool = false,
     inline_require_and_import_errors: bool = true,
     has_run_symbol_renamer: bool = false,
@@ -544,7 +546,7 @@ pub const Options = struct {
 
     module_type: options.OutputFormat = .preserve,
 
-    /// Used for cross-module inlining of import items when bundling
+    // /// Used for cross-module inlining of import items when bundling
     // const_values: Ast.ConstValuesMap = .{},
     ts_enums: Ast.TsEnumsMap = .{},
 
@@ -2146,8 +2148,10 @@ fn NewPrinter(
             return;
         }
 
-        // noop for now
-        pub inline fn printPure(_: *Printer) void {}
+        pub inline fn printPure(p: *Printer) void {
+            if (Environment.allow_assert) assert(p.options.print_dce_annotations);
+            p.printWhitespacer(ws("/* @__PURE__ */ "));
+        }
 
         pub fn printQuotedUTF8(p: *Printer, str: string, allow_backtick: bool) void {
             const quote = if (comptime !is_json)
@@ -2353,7 +2357,7 @@ fn NewPrinter(
                     }
                 },
                 .e_new => |e| {
-                    const has_pure_comment = e.can_be_unwrapped_if_unused;
+                    const has_pure_comment = e.can_be_unwrapped_if_unused and p.options.print_dce_annotations;
                     const wrap = level.gte(.call) or (has_pure_comment and level.gte(.postfix));
 
                     if (wrap) {
@@ -2403,7 +2407,7 @@ fn NewPrinter(
                         wrap = true;
                     }
 
-                    const has_pure_comment = e.can_be_unwrapped_if_unused;
+                    const has_pure_comment = e.can_be_unwrapped_if_unused and p.options.print_dce_annotations;
                     if (has_pure_comment and level.gte(.postfix)) {
                         wrap = true;
                     }

diff --git a/src/options.zig b/src/options.zig
@@ -1515,6 +1515,9 @@ pub const BundleOptions = struct {
     minify_identifiers: bool = false,
     dead_code_elimination: bool = true,
 
+    ignore_dce_annotations: bool = false,
+    emit_dce_annotations: bool = false,
+
     code_coverage: bool = false,
     debugger: bool = false,