test: introduce an e2e test asserting that bzlmod works

.github/workflows/ci.yaml

@@ -16,6 +16,12 @@ jobs:
     # The type of runner that the job will run on
     runs-on: ubuntu-latest
 
+    strategy:
+      matrix:
+        folder:
+          - "."
+          - "e2e/bzlmod"
+
     # Steps represent a sequence of tasks that will be executed as part of the job
     steps:
       # Checks-out your repository under $GITHUB_WORKSPACE, so your job can access it
@@ -33,7 +39,7 @@ jobs:
         env:
           # Bazelisk will download bazel to here
           XDG_CACHE_HOME: ~/.cache/bazel-repo
-        run: bazel --bazelrc=.github/workflows/ci.bazelrc --bazelrc=.bazelrc test //...
+        run: cd ${{ matrix.folder }}; bazel --bazelrc=$GITHUB_WORKSPACE/.github/workflows/ci.bazelrc --bazelrc=.bazelrc test //...
       - name: integration tests
         # Find all shell scripts within e2e, echo the filename, execute, fail on error
         run: find e2e/*.sh -maxdepth 1 -type f -exec sh -c 'echo "\n\n------------------------------- $0 -------------------------------" && "$0" || kill $PPID' \{\} \;

MODULE.bazel

@@ -0,0 +1,18 @@
+"aspect-build/bazel-lib"
+
+module(
+    name = "aspect_bazel_lib",
+    version = "0.0.0",
+    compatibility_level = 1,
+    toolchains_to_register = [
+        "@jq_toolchains//:all",
+        "@yq_toolchains//:all",
+    ],
+)
+
+bazel_dep(name = "bazel_skylib", version = "1.1.1")
+bazel_dep(name = "platforms", version = "0.0.4")
+
+ext = use_extension("@aspect_bazel_lib//lib:extensions.bzl", "ext")
+use_repo(ext, "jq_toolchains")
+use_repo(ext, "yq_toolchains")

WORKSPACE

@@ -25,6 +25,12 @@ local_repository(
     path = "./lib/tests/external_test_repo",
 )
 
+# Avoid descending into the e2e workspaces
+local_repository(
+    name = "e2e_bzlmod",
+    path = "./e2e/bzlmod",
+)
+
 ############################################
 # Gazelle, for generating bzl_library targets
 load("@io_bazel_rules_go//go:deps.bzl", "go_register_toolchains", "go_rules_dependencies")

e2e/bzlmod/.bazelrc

@@ -0,0 +1,2 @@
+common --experimental_enable_bzlmod
+common --registry=https://raw.githubusercontent.com/aspect-build/bazel-central-registry/main/

e2e/bzlmod/BUILD.bazel

@@ -0,0 +1,15 @@
+load("@aspect_bazel_lib//lib:jq.bzl", "jq")
+load("@bazel_skylib//rules:diff_test.bzl", "diff_test")
+
+# No sources produces null (equivalent to --null-input)
+jq(
+    name = "case_no_sources",
+    srcs = [],
+    filter = ".",
+)
+
+diff_test(
+    name = "test",
+    file1 = "case_no_sources",
+    file2 = "expected",
+)

e2e/bzlmod/MODULE.bazel

@@ -0,0 +1,13 @@
+module(
+    name = "e2e_bzlmod",
+    version = "0.0.0",
+    compatibility_level = 1,
+)
+
+bazel_dep(name = "aspect_bazel_lib", version = "0.9.8")
+bazel_dep(name = "bazel_skylib", version = "1.1.1")
+
+local_path_override(
+    module_name = "aspect_bazel_lib",
+    path = "../..",
+)

e2e/bzlmod/expected

@@ -0,0 +1 @@
+null

lib/extensions.bzl

@@ -0,0 +1,16 @@
+"Module extensions for use with bzlmod"
+
+load(
+    "@aspect_bazel_lib//lib:repositories.bzl",
+    "register_jq_toolchains",
+    "register_yq_toolchains",
+)
+
+def _toolchain_extension(_):
+    register_yq_toolchains(register = False)
+    register_jq_toolchains(register = False)
+
+# TODO: some way for users to control repo name/version of the tools installed
+ext = module_extension(
+    implementation = _toolchain_extension,
+)

lib/repositories.bzl

@@ -21,20 +21,23 @@ def aspect_bazel_lib_dependencies():
 DEFAULT_JQ_VERSION = _DEFAULT_JQ_VERSION
 DEFAULT_YQ_VERSION = _DEFAULT_YQ_VERSION
 
-def register_jq_toolchains(name = "jq", version = DEFAULT_JQ_VERSION):
+def register_jq_toolchains(name = "jq", version = DEFAULT_JQ_VERSION, register = True):
     """Registers jq toolchain and repositories
 
     Args:
         name: override the prefix for the generated toolchain repositories
         version: the version of jq to execute (see https://github.com/stedolan/jq/releases)
+        register: whether to call through to native.register_toolchains.
+            Should be True for WORKSPACE users, but false when used under bzlmod extension
     """
     for [platform, meta] in JQ_PLATFORMS.items():
         jq_platform_repo(
             name = "%s_%s" % (name, platform),
             platform = platform,
             version = version,
         )
-        native.register_toolchains("@%s_toolchains//:%s_toolchain" % (name, platform))
+        if register:
+            native.register_toolchains("@%s_toolchains//:%s_toolchain" % (name, platform))
 
     jq_host_alias_repo(
         name = "%s_host" % name,
@@ -46,20 +49,23 @@ def register_jq_toolchains(name = "jq", version = DEFAULT_JQ_VERSION):
         user_repository_name = name,
     )
 
-def register_yq_toolchains(name = "yq", version = DEFAULT_YQ_VERSION):
+def register_yq_toolchains(name = "yq", version = DEFAULT_YQ_VERSION, register = True):
     """Registers yq toolchain and repositories
 
     Args:
         name: override the prefix for the generated toolchain repositories
         version: the version of yq to execute (see https://github.com/mikefarah/yq/releases)
+        register: whether to call through to native.register_toolchains.
+            Should be True for WORKSPACE users, but false when used under bzlmod extension
     """
     for [platform, meta] in YQ_PLATFORMS.items():
         yq_platform_repo(
             name = "%s_%s" % (name, platform),
             platform = platform,
             version = version,
         )
-        native.register_toolchains("@%s_toolchains//:%s_toolchain" % (name, platform))
+        if register:
+            native.register_toolchains("@%s_toolchains//:%s_toolchain" % (name, platform))
 
     yq_host_alias_repo(
         name = "%s_host" % name,