feat: allow metafile generation to be optional (#38)

esbuild/private/esbuild.bzl

@@ -74,6 +74,11 @@ This can be useful if running many esbuild rule invocations in parallel, which h
 For general use, leave this attribute unset.
     """,
     ),
+    "metafile": attr.bool(
+        default = False,
+        doc = "If true, esbuild creates a metafile along with the output",
+        mandatory = False,
+    ),
     "minify": attr.bool(
         default = False,
         doc = """Minifies the bundle with the built in minification.
@@ -197,7 +202,7 @@ def _esbuild_impl(ctx):
         # Also disable the log limit and show all logs
         "logLevel": "warning",
         "logLimit": 0,
-        "metafile": True,
+        "metafile": ctx.attr.metafile,
         "platform": ctx.attr.platform,
         "preserveSymlinks": True,
         "sourcesContent": ctx.attr.sources_content,
@@ -269,10 +274,11 @@ def _esbuild_impl(ctx):
     inputs.append(args_file)
     launcher_args.add("--esbuild_args=%s" % args_file.short_path)
 
-    # add metafile
-    meta_file = ctx.actions.declare_file("%s_metadata.json" % ctx.attr.name)
-    outputs.append(meta_file)
-    launcher_args.add("--metafile=%s" % meta_file.short_path)
+    if ctx.attr.metafile:
+        # add metafile
+        meta_file = ctx.actions.declare_file("%s_metadata.json" % ctx.attr.name)
+        outputs.append(meta_file)
+        launcher_args.add("--metafile=%s" % meta_file.short_path)
 
     # add reference to the users args file, these are merged within the launcher
     if ctx.attr.args_file:

esbuild/private/launcher.js

@@ -118,11 +118,12 @@ async function runOneBuild(args, userArgsFilePath, configFilePath) {
     }
   }
 
-  const metafile = getFlag('--metafile')
-
   try {
     const result = await esbuild.build(args)
-    writeFileSync(metafile, JSON.stringify(result.metafile))
+    if (result.metafile) {
+      const metafile = getFlag('--metafile');
+      writeFileSync(metafile, JSON.stringify(result.metafile));
+    }
   } catch (e) {
     console.error(e)
     process.exit(1)

examples/BUILD.bazel

@@ -8,9 +8,24 @@ esbuild(
         "name.js",
     ],
     entry_point = "main.js",
+    metafile = True,
 )
 
 build_test(
     name = "test",
     targets = [":lib"],
 )
+
+sh_test(
+    name = "metafile_test",
+    size = "small",
+    srcs = [
+        "metafile_test.sh",
+    ],
+    args = [
+        "$(locations :lib)",
+    ],
+    data = [
+        ":lib",
+    ],
+)

examples/metafile_test.sh

@@ -0,0 +1,11 @@
+#!/usr/bin/env bash
+
+set -uo pipefail;
+
+while [ "$#" -ne 0 ]; do
+  [[ "lib_metadata.json" == "$(basename $1)" ]] && exit 0;
+  shift;
+done
+
+echo "Expected lib_metadata.json to be produced" >&2
+exit 1