feat: add js library as option for webpack config (#163)

Fix #161

### Changes are visible to end-users: yes

- Searched for relevant documentation and updated as needed: YES
- Breaking change (forces users to change their own code or config): NO
- Suggested release notes appear below: YES

Added option to use js_library for webpack config as alternative to files.

### Test plan

- New test cases added

e2e/loaders_jslib/.bazelignore

@@ -0,0 +1 @@
+node_modules

e2e/loaders_jslib/.bazelrc

@@ -0,0 +1,15 @@
+# Import Aspect bazelrc presets
+try-import %workspace%/../../.aspect/bazelrc/bazel7.bazelrc
+import %workspace%/../../.aspect/bazelrc/convenience.bazelrc
+import %workspace%/../../.aspect/bazelrc/correctness.bazelrc
+import %workspace%/../../.aspect/bazelrc/debug.bazelrc
+import %workspace%/../../.aspect/bazelrc/javascript.bazelrc
+import %workspace%/../../.aspect/bazelrc/performance.bazelrc
+
+### YOUR PROJECT SPECIFIC OPTIONS GO HERE ###
+
+# Load any settings & overrides specific to the current user from `.aspect/bazelrc/user.bazelrc`.
+# This file should appear in `.gitignore` so that settings are not shared with team members. This
+# should be last statement in this config so the user configuration is able to overwrite flags from
+# this file. See https://bazel.build/configure/best-practices#bazelrc-file.
+try-import %workspace%/../../.aspect/bazelrc/user.bazelrc

e2e/loaders_jslib/.bazelversion

@@ -0,0 +1 @@
+../../.bazelversion

e2e/loaders_jslib/.npmrc

@@ -0,0 +1,4 @@
+# Disabling pnpm [hoisting](https://pnpm.io/npmrc#hoist) by setting `hoist=false` is recommended on
+# projects using rules_js so that pnpm outside of Bazel lays out a node_modules tree similar to what
+# rules_js lays out under Bazel (without a hidden node_modules/.pnpm/node_modules)
+hoist=false

e2e/loaders_jslib/BUILD.bazel

@@ -0,0 +1,32 @@
+load("@aspect_rules_js//js:defs.bzl", "js_library")
+load("@aspect_rules_webpack//webpack:defs.bzl", "webpack_bundle")
+load("@bazel_skylib//rules:build_test.bzl", "build_test")
+load("@npm//:defs.bzl", "npm_link_all_packages")
+
+npm_link_all_packages(name = "node_modules")
+
+js_library(
+    name = "webpack-config",
+    srcs = ["webpack.config.cjs"],
+    deps = [
+        ":node_modules/ts-loader",
+    ],
+)
+
+webpack_bundle(
+    name = "basic",
+    srcs = [
+        "src/index.ts",
+        "tsconfig.json",
+    ],
+    node_modules = "//:node_modules",
+    output_dir = True,
+    webpack_config = ":webpack-config",
+)
+
+build_test(
+    name = "test",
+    targets = [
+        ":basic",
+    ],
+)

e2e/loaders_jslib/MODULE.bazel

@@ -0,0 +1,6 @@
+###############################################################################
+# Bazel now uses Bzlmod by default to manage external dependencies.
+# Please consider migrating your external dependencies from WORKSPACE to MODULE.bazel.
+#
+# For more details, please check https://github.com/bazelbuild/bazel/issues/18958
+###############################################################################

e2e/loaders_jslib/WORKSPACE

@@ -0,0 +1,33 @@
+# Override http_archive for local testing
+local_repository(
+    name = "aspect_rules_webpack",
+    path = "../..",
+)
+
+# Fetch the Bazel module dependencies
+
+load("@aspect_rules_webpack//webpack:dependencies.bzl", "rules_webpack_dependencies")
+
+rules_webpack_dependencies()
+
+# Fetch and register a nodejs interpreter, if you haven't already
+
+load("@aspect_rules_js//js:toolchains.bzl", "DEFAULT_NODE_VERSION", "rules_js_register_toolchains")
+
+rules_js_register_toolchains(node_version = DEFAULT_NODE_VERSION)
+
+# brought as a dep by webpack ruleset
+load("@aspect_rules_js//npm:repositories.bzl", "npm_translate_lock")
+
+npm_translate_lock(
+    name = "npm",
+    no_optional = True,
+    npmrc = "//:.npmrc",
+    pnpm_lock = "//:pnpm-lock.yaml",
+    pnpm_version = "9.0.0",
+    verify_node_modules_ignored = "//:.bazelignore",
+)
+
+load("@npm//:repositories.bzl", "npm_repositories")
+
+npm_repositories()

e2e/loaders_jslib/package.json

@@ -0,0 +1,11 @@
+{
+  "devDependencies": {
+    "ts-loader": "9.4.2",
+    "typescript": "4.8.4",
+    "webpack": "5.76.2",
+    "webpack-cli": "5.0.1"
+  },
+  "pnpm": {
+    "onlyBuiltDependencies": []
+  }
+}