Enable Bzlmod

Fulfills most of bazelbuild#1482. Compatible with Bazel 6.5.0 and 7.5.0, but not
Bazel 8.

New `MODULE.bazel` files mirroring existing `WORKSPACE` configurations
comprise the bulk of the commit. The empty `WORKSPACE.bzlmod` files
ensure that Bzlmod won't evaluate the existing `WORKSPACE` files.

These new files comprise the most significant part of the change:

- scala/extensions/config.bzl
- scala/extensions/deps.bzl
- scala/private/extensions/dev_deps.bzl
- scala/private/macros/bzlmod.bzl
- scala/private/macros/test/BUILD.bzlmod_test
- scala/private/macros/test/MODULE.bzlmod_test
- scala/private/macros/test/bzlmod_test_ext.bzl
- test/shell/test_bzlmod_macros.sh

The pattern employed throughout the new module extensions is explained
in the `scala/private/macros/bzlmod.bzl` docstring. Adding
`test/shell/test_bzlmod_macros.sh` also precipitated adding a new
`assert_matches` helper to `test/shell/test_helper.sh`.

"Publish to BCR" configuration will come in a future commit. After that,
we can publish a new major version and then close bazelbuild#1482.

Per bazelbuild#1647, `com_google_protobuf` remains at v21.7, and versions up to
v25.5 can work after bumping `com_google_absl` to 20240722.0 and setting
C++17 compiler flags in `.bazelrc`.

This change enables Bazel 6 and 7 users to migrate their `rules_scala`
dependency from `WORKSPACE` to `MODULE.bazel` whenever they're ready.

After the next major version release includes this change, we can update
`com_google_protobuf`, `rules_java`, and related dependencies as part of
enabling Bazel 8 compatibility (bazelbuild#1652). The `rules_jvm_external` update
in that change will effectively end Bzlmod support for Bazel 6.5.0,
requiring another major version release after that.

.bazelignore

@@ -0,0 +1,6 @@
+# Remove once the following is fixed:
+# - bazelbuild/bazel: Loading top-level targets in local_path_override modules
+#   in child directory breaks the build #22208
+#   https://github.com/bazelbuild/bazel/issues/22208
+third_party/test/example_external_workspace
+third_party/test/proto

.bazelrc

@@ -1,9 +1,7 @@
+common --enable_bzlmod
+
 build --enable_platform_specific_config
 
 #Windows needs --worker_quit_after_build due to workers not being shut down when the compiler tools need to be rebuilt (resulting in 'file in use' errors). See Bazel Issue#10498.
 
 build:windows --worker_quit_after_build --enable_runfiles 
-
-# Remove upon completing Bzlmod compatibility work.
-# - https://github.com/bazelbuild/rules_scala/issues/1482
-build --noenable_bzlmod

.gitignore

@@ -16,3 +16,9 @@ test/semanticdb/tempsrc
 
 # From scripts/create_repository.py
 repository-artifacts.json
+
+# Until it settles down
+**/MODULE.bazel.lock
+
+# Used by some tests, but can also be used for local experimentation.
+tmp/

MODULE.bazel

@@ -0,0 +1,290 @@
+"""Bazel module definition for rules_scala"""
+
+module(
+    name = "rules_scala",
+    version = "7.0.0",
+    compatibility_level = 7,
+    bazel_compatibility = [">=6.5.0", "<8.0.0"],
+)
+
+SCALA_VERSION = "2.12.20"
+
+# These versions match those required by some tests, including
+# test_thirdparty_version.sh.
+SCALA_2_VERSIONS = [
+    "2.11.12",
+    "2.12.20",
+    "2.13.15",
+]
+
+SCALA_3_VERSIONS = [
+    "3.1.3",
+    "3.3.5",
+    "3.5.2",
+    "3.6.3",
+]
+
+SCALA_VERSIONS = SCALA_2_VERSIONS + SCALA_3_VERSIONS
+
+bazel_dep(name = "bazel_skylib", version = "1.7.1")
+
+# Bazel 6 breaks with any higher version of `rules_cc`, because:
+# - 0.0.10 requires Bazel 7 to define `CcSharedLibraryHintInfo`
+# - 0.0.13 and up don't support `protobuf` v21.7, requiring at least v27.0
+# - 0.1.0 should work, but requires `stardoc` 0.7.0, which requires Bazel 7
+#   (though it's a `dev_dependency`, it still gets pulled in during analysis,
+#   breaking the build)
+bazel_dep(name = "rules_cc", version = "0.0.9")
+single_version_override(
+    module_name = "rules_cc",
+    version = "0.0.9",
+)
+
+bazel_dep(name = "rules_java", version = "7.12.4")
+bazel_dep(name = "rules_proto", version = "6.0.2")
+
+# For now, users are revlocked to protobuf-21.7 or protobuf-25.5 (which doesn't
+# build under Bazel 6).
+bazel_dep(
+    name = "protobuf",
+    version = "21.7",
+    repo_name = "com_google_protobuf",
+)
+single_version_override(
+    module_name = "protobuf",
+    version = "21.7",
+)
+
+scala_config = use_extension(
+    "//scala/extensions:config.bzl",
+    "scala_config",
+)
+use_repo(scala_config, "io_bazel_rules_scala_config")
+
+dev_config = use_extension(
+    "//scala/extensions:config.bzl",
+    "scala_config",
+    dev_dependency = True,
+)
+dev_config.settings(
+    enable_compiler_dependency_tracking = True,
+    scala_version = SCALA_VERSION,
+    scala_versions = SCALA_VERSIONS,
+)
+
+scala_deps = use_extension("//scala/extensions:deps.bzl", "scala_deps")
+
+# Register some of our testing toolchains first when building our repo.
+register_toolchains(
+    "//scala:unused_dependency_checker_error_toolchain",
+    "//test/proto:scalapb_toolchain",
+    "//test/toolchains:java21_toolchain_definition",
+    dev_dependency = True,
+)
+
+use_repo(
+    scala_deps,
+    "rules_scala_toolchains",
+    "scala_compiler_sources",
+)
+
+register_toolchains("@rules_scala_toolchains//...:all")
+
+# Dev dependencies
+
+dev_deps = use_extension(
+    "//scala/extensions:deps.bzl",
+    "scala_deps",
+    dev_dependency = True,
+)
+dev_deps.toolchains(
+    jmh = True,
+    scala_proto = True,
+    #scala_proto_enable_all_options = True,
+    scalafmt = True,
+    testing = True,
+    #scalatest = True,
+    #junit = True,
+    #specs2 = True,
+    twitter_scrooge = True,
+)
+
+use_repo(
+    dev_deps,
+    "scala_proto_rules_scalapb_compilerplugin",
+    "scala_proto_rules_scalapb_protoc_bridge",
+    "scalafmt_default",
+)
+
+# Default versions of version specific repos needed by some of our tests. Tests
+# that set `--repo_env=SCALA_VERSION=...` break without using the default here,
+# because version specific repos for other versions won't be available.
+use_repo(
+    dev_deps,
+    "io_bazel_rules_scala_guava",
+    "io_bazel_rules_scala_junit_junit",
+    "io_bazel_rules_scala_scala_compiler",
+    "io_bazel_rules_scala_scala_library",
+)
+
+[
+    [
+        use_repo(dev_deps, dep + "_" + scala_version.replace(".", "_"))
+        for dep in [
+            "io_bazel_rules_scala_junit_junit",
+            "io_bazel_rules_scala_scala_compiler",
+            "io_bazel_rules_scala_scala_library",
+        ] + (
+            # We can remove this condition once we drop support for Scala 2.11.
+            ["scala_proto_rules_scalapb_protoc_gen"]
+            if not scala_version.startswith("2.11.") else []
+        )
+    ]
+    for scala_version in SCALA_VERSIONS
+]
+
+[
+    [
+        use_repo(dev_deps, dep + "_" + scala_version.replace(".", "_"))
+        for dep in [
+            "io_bazel_rules_scala_scala_reflect",
+        ]
+    ]
+    for scala_version in SCALA_2_VERSIONS
+]
+
+[
+    [
+        use_repo(dev_deps, dep + "_" + scala_version.replace(".", "_"))
+        for dep in [
+            "io_bazel_rules_scala_scala_compiler_2",
+            "io_bazel_rules_scala_scala_library_2",
+            "io_bazel_rules_scala_scala_reflect_2",
+        ]
+    ]
+    for scala_version in SCALA_3_VERSIONS
+]
+
+internal_dev_deps = use_extension(
+    "//scala/private/extensions:dev_deps.bzl",
+    "dev_deps",
+    dev_dependency = True,
+)
+
+# See //scala/private:extensions/dev_deps.bzl for notes on some of these repos.
+use_repo(
+    internal_dev_deps,
+    "com_github_bazelbuild_buildtools",
+    "com_github_jnr_jffi_native",
+    "com_google_guava_guava_21_0",
+    "com_google_guava_guava_21_0_with_file",
+    "com_twitter__scalding_date",
+    "org_apache_commons_commons_lang_3_5",
+    "org_apache_commons_commons_lang_3_5_without_file",
+    "org_springframework_spring_core",
+    "org_springframework_spring_tx",
+    "org_typelevel__cats_core",
+    "org_typelevel_kind_projector",
+)
+
+java_toolchains = use_extension(
+    "@rules_java//java:extensions.bzl",
+    "toolchains",
+    dev_dependency = True,
+)
+
+use_repo(
+    java_toolchains,
+    # //test/toolchains:java21_toolchain
+    "remotejdk21_linux",
+    "remotejdk21_macos",
+    "remotejdk21_win",
+    # //test/jmh:test_jmh_jdk8
+    "remote_jdk8_linux",
+    "remote_jdk8_macos",
+    "remote_jdk8_windows",
+)
+
+[
+    (
+        bazel_dep(name = name, dev_dependency = True),
+        local_path_override(module_name = name, path = path)
+    )
+    for name, path in [
+        (
+            "proto_cross_repo_boundary",
+            "test/proto_cross_repo_boundary/repo",
+        ),
+        (
+            "test_new_local_repo",
+            "third_party/test/new_local_repo",
+        ),
+        (
+            "example_external_workspace",
+            "third_party/test/example_external_workspace",
+        ),
+    ]
+]
+
+bazel_dep(
+    name = "platforms",
+    version = "0.0.11",
+    dev_dependency = True,
+)
+bazel_dep(
+    name = "bazel_ci_rules",
+    version = "1.0.0",
+    dev_dependency = True,
+    repo_name = "bazelci_rules",
+)
+bazel_dep(
+    name = "rules_go",
+    version = "0.53.0",
+    dev_dependency = True,
+    repo_name = "io_bazel_rules_go", # for com_github_bazelbuild_buildtools
+)
+bazel_dep(name = "gazelle", version = "0.42.0", dev_dependency = True)
+
+go_sdk = use_extension(
+    "@io_bazel_rules_go//go:extensions.bzl",
+    "go_sdk",
+    dev_dependency = True,
+)
+go_sdk.download(version = "1.24.0")
+
+go_deps = use_extension(
+    "@gazelle//:extensions.bzl",
+    "go_deps",
+    dev_dependency = True,
+)
+
+# The go_deps.module calls are inspired by the following to get the
+# com_github_bazelbuild_buildtools repo to work:
+#
+# - https://github.com/bazelbuild/bazel-central-registry/blob/main/modules/gazelle/0.39.1/MODULE.bazel#L31-L57
+#
+# To get the latest version and hashes for each per:
+#
+# - https://go.dev/ref/mod#go-list-m
+# - https://go.dev/ref/mod#checksum-database
+#
+#   go list -m golang.org/x/tools@latest
+#   curl https://sum.golang.org/lookup/golang.org/x/[email protected]
+go_deps.module(
+    path = "golang.org/x/tools",
+    sum = "h1:BgcpHewrV5AUp2G9MebG4XPFI1E2W41zU1SaqVA9vJY=",
+    version = "v0.30.0",
+)
+
+go_deps.module(
+    path = "github.com/golang/protobuf",
+    sum = "h1:i7eJL8qZTpSEXOPTxNKhASYpMn+8e5Q6AdndVa1dWek=",
+    version = "v1.5.4",
+)
+use_repo(
+    go_deps,
+    "com_github_golang_protobuf",
+    "org_golang_x_tools",
+)
+
+bazel_dep(name = "rules_python", version = "0.38.0", dev_dependency = True)

dt_patches/compiler_sources/MODULE.bazel

@@ -0,0 +1,15 @@
+"""Bazel module ./test/shell/test_examples.sh tests"""
+
+module(name = "compiler_sources")
+
+bazel_dep(name = "rules_scala")
+local_path_override(
+    module_name = "rules_scala",
+    path = "../..",
+)
+
+scala_config = use_extension(
+    "@rules_scala//scala/extensions:config.bzl",
+    "scala_config",
+)
+use_repo(scala_config, "io_bazel_rules_scala_config")

dt_patches/compiler_sources/extensions.bzl

@@ -61,3 +61,10 @@ def import_compiler_source_repos():
             licenses = ["notice"],
             server_urls = default_maven_server_urls(),
         )
+
+def _compiler_source_repos_impl(_ctx):
+    import_compiler_source_repos()
+
+compiler_source_repos = module_extension(
+    implementation = _compiler_source_repos_impl,
+)

dt_patches/test_dt_patches/BUILD

@@ -17,7 +17,9 @@ SCALA_LIBS = ["@scala_library"] + select_for_scala_version(
 
 setup_scala_toolchain(
     name = "dt_scala_toolchain",
+    parser_combinators_deps = [],
     scala_compile_classpath = ["@scala_compiler"] + SCALA_LIBS,
     scala_library_classpath = SCALA_LIBS,
     scala_macro_classpath = SCALA_LIBS,
+    scala_xml_deps = [],
 )