feat(rollup): support esm configurations to be provided

docs/Rollup.md

@@ -347,7 +347,7 @@ Defaults to `@npm//@bazel/rollup/bin:rollup-worker`
 
 (*Boolean*): Whether to execute the rollup binary with the --silent flag, defaults to False.
 
-Using --silent can cause rollup to [ignore errors/warnings](https://github.com/rollup/rollup/blob/master/docs/999-big-list-of-options.md#onwarn) 
+Using --silent can cause rollup to [ignore errors/warnings](https://github.com/rollup/rollup/blob/master/docs/999-big-list-of-options.md#onwarn)
 which are only surfaced via logging.  Since bazel expects printing nothing on success, setting silent to True
 is a more Bazel-idiomatic experience, however could cause rollup to drop important warnings.
 

npm_deps.bzl

@@ -24,6 +24,8 @@ def npm_deps():
             "//tools/npm_packages/bazel_workspaces_consistent:BUILD.bazel",
             "//tools/npm_packages/bazel_workspaces_consistent:index.bzl",
             "//tools/npm_packages/bazel_workspaces_consistent:package.json",
+            "//:tools/npm_packages/test_esm_pkg/package.json",
+            "//:tools/npm_packages/test_esm_pkg/index.mjs",
             "//:tools/npm_packages/hello/package.json",
             "//:tools/npm_packages/hello/index.js",
             "//:tools/npm_packages/node_resolve_index/index.js",
@@ -91,6 +93,8 @@ js_library(
             "//tools/npm_packages/bazel_workspaces_consistent:BUILD.bazel",
             "//tools/npm_packages/bazel_workspaces_consistent:index.bzl",
             "//tools/npm_packages/bazel_workspaces_consistent:package.json",
+            "//:tools/npm_packages/test_esm_pkg/package.json",
+            "//:tools/npm_packages/test_esm_pkg/index.mjs",
             "//:tools/npm_packages/hello/package.json",
             "//:tools/npm_packages/hello/index.js",
             "//:tools/npm_packages/node_resolve_index/index.js",

package.json

@@ -92,6 +92,7 @@
         "source-map": "^0.7.3",
         "source-map-support": "0.5.9",
         "terser": "4.4.0",
+        "test_esm_pkg": "file:./tools/npm_packages/test_esm_pkg",
         "testy": "file:./tools/npm_packages/testy",
         "tmp": "0.1.0",
         "ts-lit-plugin": "1.1.9",

packages/rollup/rollup_bundle.bzl

@@ -135,7 +135,7 @@ Otherwise, the outputs are assumed to be a single file.
     "silent": attr.bool(
         doc = """Whether to execute the rollup binary with the --silent flag, defaults to False.
 
-Using --silent can cause rollup to [ignore errors/warnings](https://github.com/rollup/rollup/blob/master/docs/999-big-list-of-options.md#onwarn) 
+Using --silent can cause rollup to [ignore errors/warnings](https://github.com/rollup/rollup/blob/master/docs/999-big-list-of-options.md#onwarn)
 which are only surfaced via logging.  Since bazel expects printing nothing on success, setting silent to True
 is a more Bazel-idiomatic experience, however could cause rollup to drop important warnings.
 """,
@@ -312,7 +312,8 @@ def _rollup_bundle(ctx):
 
     stamp = ctx.attr.stamp[StampSettingInfo].value
 
-    config = ctx.actions.declare_file("_%s.rollup_config.js" % ctx.label.name)
+    config_extension = ctx.file.config_file.extension
+    config = ctx.actions.declare_file("_%s.rollup_config.%s" % (ctx.label.name, config_extension))
     ctx.actions.expand_template(
         template = ctx.file.config_file,
         output = config,

packages/rollup/test/esm_config/BUILD.bazel

@@ -0,0 +1,20 @@
+load("@build_bazel_rules_nodejs//:index.bzl", "generated_file_test")
+load("//packages/rollup:index.bzl", "rollup_bundle")
+
+rollup_bundle(
+    name = "esm_config",
+    config_file = "rollup.config.mjs",
+    entry_point = "input.js",
+    sourcemap = "false",
+    supports_workers = True,
+    deps = [
+        # Fake test ESM package from `npm_deps.bzl`.
+        "@npm//test_esm_pkg",
+    ],
+)
+
+generated_file_test(
+    name = "test",
+    src = "golden.js_",
+    generated = ":esm_config.js",
+)

packages/rollup/test/esm_config/golden.js_

@@ -0,0 +1 @@
+console.log('Works - test fixture');

packages/rollup/test/esm_config/input.js

@@ -0,0 +1 @@
+console.log('Works - test fixture');

packages/rollup/test/esm_config/rollup.config.mjs

@@ -0,0 +1,7 @@
+// Note: We want to have some actual import statements here,
+// validating that ESM is actually used for this config file.
+import 'test_esm_pkg';
+
+export default {
+  plugins: [],
+};

tools/npm_packages/test_esm_pkg/index.mjs

@@ -0,0 +1 @@
+export const greetings = 'Hello';

tools/npm_packages/test_esm_pkg/package.json

@@ -0,0 +1,8 @@
+{
+  "version": "0.0.1",
+  "exports": {
+    ".": {
+      "import": "./index.mjs"
+    }
+  }
+}

yarn.lock

@@ -10367,6 +10367,9 @@ test-exclude@^6.0.0:
     glob "^7.1.4"
     minimatch "^3.0.4"
 
+"test_esm_pkg@file:./tools/npm_packages/test_esm_pkg":
+  version "0.0.1"
+
 "testy@file:./tools/npm_packages/testy":
   version "0.0.1"