feat(esbuild): add output_css flag to esbuild() (#2545)

packages/esbuild/esbuild.bzl

@@ -28,6 +28,9 @@ def _esbuild_impl(ctx):
         elif hasattr(dep, "files"):
             deps_depsets.append(dep.files)
 
+        if DefaultInfo in dep:
+            deps_depsets.append(dep[DefaultInfo].data_runfiles.files)
+
         if NpmPackageInfo in dep:
             deps_depsets.append(dep[NpmPackageInfo].sources)
             npm_workspaces.append(dep[NpmPackageInfo].workspace)
@@ -100,6 +103,9 @@ def _esbuild_impl(ctx):
                 fail("output_map must be specified if sourcemap is not set to 'inline'")
             outputs.append(js_out_map)
 
+        if ctx.outputs.output_css:
+            outputs.append(ctx.outputs.output_css)
+
         if ctx.attr.format:
             args.add_joined(["--format", ctx.attr.format], join_with = "=")
 
@@ -219,6 +225,14 @@ See https://esbuild.github.io/api/#splitting for more details
             mandatory = False,
             doc = "Name of the output source map when bundling",
         ),
+        "output_css": attr.output(
+            mandatory = False,
+            doc = """Declare a .css file will be output next to output bundle.
+
+If your JS code contains import statements that import .css files, esbuild will place the
+content in a file next to the main output file, which you'll need to declare. If your output
+file is named 'foo.js', you should set this to 'foo.css'.""",
+        ),
         "platform": attr.string(
             default = "browser",
             values = ["node", "browser", "neutral", ""],

packages/esbuild/test/css/BUILD.bazel

@@ -0,0 +1,67 @@
+load("//packages/esbuild/test:tests.bzl", "esbuild")
+load("//packages/jasmine:index.bzl", "jasmine_node_test")
+load("//packages/typescript:index.bzl", "ts_library")
+load("@build_bazel_rules_nodejs//:index.bzl", "copy_to_bin")
+
+copy_to_bin(
+    name = "external_copied",
+    srcs = ["external.css"],
+)
+
+ts_library(
+    name = "dep",
+    srcs = [
+        "dep.ts",
+    ],
+    data = [
+        ":external_copied",
+    ],
+    deps = [
+        "@npm//@types/node",
+    ],
+)
+
+ts_library(
+    name = "main",
+    srcs = [
+        "main.ts",
+    ],
+    deps = [
+        ":dep",
+        "@npm//@types/node",
+    ],
+)
+
+esbuild(
+    name = "default",
+    args = [
+        "--keep-names",
+        "--resolve-extensions=.mjs,.js",
+    ],
+    entry_point = "main.ts",
+    deps = [
+        ":main",
+    ],
+)
+
+esbuild(
+    name = "with_css",
+    args = [
+        "--keep-names",
+        "--resolve-extensions=.mjs,.js",
+    ],
+    entry_point = "main.ts",
+    output_css = "with_css.css",
+    deps = [
+        ":main",
+    ],
+)
+
+jasmine_node_test(
+    name = "bundle_test",
+    srcs = ["bundle_test.js"],
+    data = [
+        ":default",
+        ":with_css",
+    ],
+)

packages/esbuild/test/css/bundle_test.js

@@ -0,0 +1,25 @@
+const { readFileSync } = require("fs");
+const path = require("path");
+
+const helper = require(process.env.BAZEL_NODE_RUNFILES_HELPER);
+const locationBase = "build_bazel_rules_nodejs/packages/esbuild/test/css/";
+
+const cssExpected = helper.resolve(path.join(locationBase, "with_css.css"));
+
+describe("esbuild css", () => {
+  it("no css by default", () => {
+    if (process.platform === "win32") {
+      // Windows has no sandbox, and the runfiles helper will return files
+      // that happen to exist in the folder, even if they are not declared outputs
+      return;
+    }
+    expect(() =>
+      helper.resolve(path.join(locationBase, "default.css"))
+    ).toThrow();
+  });
+
+  it("css if requested", () => {
+    const contents = readFileSync(cssExpected, { encoding: "utf8" });
+    expect(contents).toContain("external-content");
+  });
+});

packages/esbuild/test/css/dep.ts

@@ -0,0 +1,3 @@
+import "./external.css";
+
+export function dep() {}

packages/esbuild/test/css/external.css

@@ -0,0 +1,2 @@
+.external-content {
+}

packages/esbuild/test/css/main.ts

@@ -0,0 +1,3 @@
+import { dep } from "./dep";
+
+dep();