Start using bzlmod

.bazelrc

@@ -1,6 +1,11 @@
 # Always tell why tests fail
 test --test_output=errors
 
+# We use Bazel's modern dependency management system. This works for us only with Bazel >= 6.2.0
+# This is the deprecated version. "--enable_bzlmod" is the forward path. However, as Bazel < 6.0.0 does not support the
+# new flag. We keep using the deprecated one until we no longer support Bazel 5.
+build --experimental_enable_bzlmod=true
+
 # Mypy integration
 build:mypy --aspects=@mypy_integration//:mypy.bzl%mypy_aspect
 build:mypy --output_groups=mypy

.bazelversion

@@ -1 +1 @@
-6.2.0
+6.4.0

.pre-commit-config.yaml

@@ -21,7 +21,7 @@ repos:
         additional_dependencies:
           - mdformat-gfm
   - repo: https://github.com/keith/pre-commit-buildifier
-    rev: 6.3.3.1
+    rev: 6.4.0
     hooks:
       - id: buildifier
         args: [ "--warnings=+out-of-order-load,+unsorted-dict-items,+native-py" ]

MODULE.bazel

@@ -0,0 +1,117 @@
+module(
+    name = "depend_on_what_you_use",
+    bazel_compatibility = [">=5.4.0"],
+    compatibility_level = 0,
+)
+
+bazel_dep(
+    name = "bazel_skylib",
+    # Keep in sync with //third_party/dependencies.bzl
+    version = "1.5.0",
+)
+bazel_dep(
+    name = "rules_python",
+    # Keep in sync with //third_party/dependencies.bzl
+    version = "0.27.0",
+)
+
+pip = use_extension("@rules_python//python/extensions:pip.bzl", "pip")
+pip.parse(
+    hub_name = "dwyu_py_deps",
+    python_version = "3.10",
+    requirements_lock = "//third_party:requirements.txt",
+)
+use_repo(pip, "dwyu_py_deps")
+
+###
+### Development Dependencies
+###
+
+# Update with each rules_python update for easy lookup until specifying the patch version for toolchain is possible again
+# Keep in syc with test/aspect/execute_tests.py
+# PATCH_MAPPING:
+#  "3.10": "3.10.13"
+#  "3.11": "3.11.6"
+#  "3.12": "3.12.0"
+#  "3.8": "3.8.18"
+#  "3.9": "3.9.18"
+# Choose different version via: --@rules_python//python/config_settings:python_version=Major.Minor.Patch mathing one of
+# the registered toolchains below.
+python = use_extension(
+    "@rules_python//python/extensions:python.bzl",
+    "python",
+    dev_dependency = True,
+)
+python.toolchain(
+    python_version = "3.8",
+)
+python.toolchain(
+    python_version = "3.9",
+)
+python.toolchain(
+    is_default = True,
+    python_version = "3.10",
+)
+python.toolchain(
+    python_version = "3.11",
+)
+python.toolchain(
+    python_version = "3.12",
+)
+
+pip_dev = use_extension(
+    "@rules_python//python/extensions:pip.bzl",
+    "pip",
+    dev_dependency = True,
+)
+pip_dev.parse(
+    hub_name = "dwyu_mypy_deps",
+    python_version = "3.10",
+    requirements_lock = "//third_party:mypy_requirements.txt",
+)
+use_repo(pip_dev, "dwyu_mypy_deps")
+
+non_module_dependencies = use_extension(
+    "//third_party:extensions.bzl",
+    "non_module_dependencies",
+    dev_dependency = True,
+)
+use_repo(non_module_dependencies, "mypy_integration")
+
+bazel_dep(
+    name = "external_test_repo",
+    version = "0.0.0",
+    dev_dependency = True,
+)
+local_path_override(
+    module_name = "external_test_repo",
+    path = "test/aspect/external_repo/repo",
+)
+
+bazel_dep(
+    name = "complex_includes_test_repo",
+    version = "0.0.0",
+    dev_dependency = True,
+)
+local_path_override(
+    module_name = "complex_includes_test_repo",
+    path = "test/aspect/complex_includes/ext_repo",
+)
+
+###
+### The Migration phase using WORKSPACE.bzlmod and MODULE.bazel together does not support properly loading the implicit
+### Bazel dependencies. Thus, we need to load some basic things directly. This should become superfluous when we are
+### only using bzlmod eventually
+### Reference https://github.com/bazelbuild/bazel/blob/master/src/MODULE.tools
+###
+
+bazel_dep(
+    name = "platforms",
+    version = "0.0.7",
+    dev_dependency = True,
+)
+bazel_dep(
+    name = "rules_cc",
+    version = "0.0.1",
+    dev_dependency = True,
+)

dev_setup_step_2.bzl

@@ -19,10 +19,10 @@ def dev_setup_step_2():
     # Choose different version via: --@rules_python//python/config_settings:python_version=X
     python_register_multi_toolchains(
         name = "python",
-        default_version = "3.10.9",
+        default_version = "3.10",
         python_versions = [
-            "3.8.15",
-            "3.9.16",
-            "3.11.1",
+            "3.8",
+            "3.9",
+            "3.11",
         ],
     )

test/aspect/complex_includes/BUILD

@@ -19,5 +19,5 @@ cc_library(
 cc_library(
     name = "use_complex_includes_from_extern",
     srcs = ["use_complex_includes.cpp"],
-    deps = ["@complex_includes_repo//:complex_includes"],
+    deps = ["@complex_includes_test_repo//:complex_includes"],
 )

test/aspect/complex_includes/ext_repo.bzl

@@ -1,6 +1,6 @@
 # buildifier: disable=unnamed-macro
 def load_complex_includes_repo():
     native.local_repository(
-        name = "complex_includes_repo",
+        name = "complex_includes_test_repo",
         path = "test/aspect/complex_includes/ext_repo",
     )

test/aspect/complex_includes/ext_repo/MODULE.bazel

@@ -0,0 +1 @@
+module(name = "complex_includes_test_repo")

test/aspect/execute_tests.py

@@ -13,24 +13,32 @@
 
 # Test matrix. We don't combine each Bazel version with each Python version as there is no significant benefit. We
 # manually define pairs which make sure each Bazel and Python version we care about is used at least once.
+# Keep in sync with MODULE.bazel
 TESTED_VERSIONS = [
-    TestedVersions(bazel="5.4.1", python="3.8.15"),
-    TestedVersions(bazel="6.0.0", python="3.9.16"),
-    TestedVersions(bazel="6.4.0", python="3.10.9"),
-    TestedVersions(bazel="7.0.0rc5", python="3.11.1"),
-    TestedVersions(bazel="8.0.0-pre.20231030.2", python="3.11.1"),
+    TestedVersions(bazel="5.4.1", python="3.8.18"),
+    TestedVersions(bazel="6.0.0", python="3.9.18"),
+    TestedVersions(bazel="6.4.0", python="3.10.13"),
+    TestedVersions(bazel="7.0.0", python="3.11.6"),
+    TestedVersions(bazel="8.0.0-pre.20231030.2", python="3.12.0"),
 ]
 
 # When Bazel 7.0.0 releases we have to look again at the flags and check if more flags are available
 VERSION_SPECIFIC_ARGS = {
+    # We support Bazel's modern dependency management system, but it works only as desired with a recent Bazel version
+    "--experimental_enable_bzlmod=false": CompatibleVersions(max="6.1.99"),
+    # We are not yet sure if we really want to lock the bzlmod resolution down given we test with various Bazel versions
+    # and configurations. It seems the main benefits of the lock file are not having to reanalyze the central registry
+    # when working without a cached workspace and being safeguarded against changed or yanked modules in the central
+    # registry. Both don't matter much to us right now.
+    "--lockfile_mode=off": CompatibleVersions(min="6.2.0"),
+    # Incompatible changes
     "--incompatible_legacy_local_fallback=false": CompatibleVersions(min="5.0.0"),  # false is the forward path behavior
     "--incompatible_enforce_config_setting_visibility": CompatibleVersions(min="5.0.0"),
     "--incompatible_config_setting_private_default_visibility": CompatibleVersions(min="5.0.0"),
     "--incompatible_disable_target_provider_fields": CompatibleVersions(min="5.0.0"),
     "--incompatible_struct_has_no_methods": CompatibleVersions(min="5.0.0"),
     "--incompatible_use_platforms_repo_for_constraints": CompatibleVersions(min="5.0.0", max="6.99.99"),
     "--incompatible_disallow_empty_glob": CompatibleVersions(min="5.0.0"),
-    "--incompatible_existing_rules_immutable_view": CompatibleVersions(min="5.0.0"),
     "--incompatible_no_implicit_file_export": CompatibleVersions(min="5.0.0"),
     "--incompatible_use_cc_configure_from_rules_cc": CompatibleVersions(min="5.0.0"),
     "--incompatible_default_to_explicit_init_py": CompatibleVersions(min="5.0.0"),
@@ -40,8 +48,13 @@
     "--incompatible_sandbox_hermetic_tmp": CompatibleVersions(min="6.0.0"),
     "--incompatible_check_testonly_for_output_files": CompatibleVersions(min="6.0.0"),
     "--incompatible_check_visibility_for_toolchains": CompatibleVersions(min="7.0.0"),
+    "--incompatible_auto_exec_groups": CompatibleVersions(min="7.0.0"),
+    "--incompatible_disable_non_executable_java_binary": CompatibleVersions(min="7.0.0"),
+    # TODO for us to work on those:
+    # "--incompatible_stop_exporting_language_modules": CompatibleVersions(min="5.0.0"),
     # Theoretically interesting for our project, but Bazel itself does not adhere to it
     # "--incompatible_python_disallow_native_rules": CompatibleVersions(min="7.0.0"),
+    # Theoretically of interest for us, but rules_python does not comply to this.
     # "--incompatible_disallow_struct_provider_syntax": CompatibleVersions(min="7.0.0"),
 }
 
@@ -239,7 +252,7 @@
     ),
     TestCase(
         name="complex_includes_in_ext_repo",
-        cmd=TestCmd(target="@complex_includes_repo//...", aspect=DEFAULT_ASPECT),
+        cmd=TestCmd(target="@complex_includes_test_repo//...", aspect=DEFAULT_ASPECT),
         expected=ExpectedResult(success=True),
     ),
     TestCase(

test/aspect/external_repo/BUILD

@@ -2,7 +2,7 @@ cc_library(
     name = "use_external_libs",
     hdrs = ["use_external_libs.h"],
     deps = [
-        "@ext_repo//:ext_bar",
-        "@ext_repo//:ext_foo",
+        "@external_test_repo//:ext_bar",
+        "@external_test_repo//:ext_foo",
     ],
 )

test/aspect/external_repo/repo.bzl

@@ -1,6 +1,6 @@
 # buildifier: disable=unnamed-macro
 def load_external_repo():
     native.local_repository(
-        name = "ext_repo",
+        name = "external_test_repo",
         path = "test/aspect/external_repo/repo",
     )

test/aspect/external_repo/repo/MODULE.bazel

@@ -0,0 +1 @@
+module(name = "external_test_repo")

third_party/dependencies.bzl

@@ -2,6 +2,7 @@ load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
 load("@bazel_tools//tools/build_defs/repo:utils.bzl", "maybe")
 
 def dependencies():
+    # Keep in sync with MODULE.bazel
     rules_python_version = "0.27.0"
     maybe(
         http_archive,
@@ -11,6 +12,7 @@ def dependencies():
         urls = ["https://github.com/bazelbuild/rules_python/releases/download/{v}/rules_python-{v}.tar.gz".format(v = rules_python_version)],
     )
 
+    # Keep in sync with MODULE.bazel
     skylib_version = "1.5.0"
     http_archive(
         name = "bazel_skylib",

third_party/extensions.bzl

@@ -0,0 +1,8 @@
+load("//third_party:dev_dependencies.bzl", "dev_dependencies")
+
+def _non_module_dependencies_impl(_ctx):
+    dev_dependencies()
+
+non_module_dependencies = module_extension(
+    implementation = _non_module_dependencies_impl,
+)