[tools] Finish porting to bzlmod

Specifically, respell the "download buildifier release binaries from github"
into something bzlmod is happy with.

While we're here, also remove custom upgrade scripting for `bazel`.
Dependabot handles that upgrade automation for us now.

.bazelrc

@@ -5,10 +5,6 @@ common --keep_going=yes
 build --test_output=errors
 build --test_summary=terse
 
-# TODO(jwnimmer-tri) For the moment, we still need WORKSPACE.bzlmod.
-# Once we can delete that file, we should remove the next line as well.
-common --enable_workspace=true
-
 # Add `bazel test --config=lint` shortcut for linting.
 build:lint --test_tag_filters=lint
 

BUILD.bazel

@@ -24,7 +24,6 @@ bazel_lint_test(
     srcs = [
         "BUILD.bazel",
         "MODULE.bazel",
-        "WORKSPACE.bzlmod",
     ],
 )
 

MODULE.bazel

@@ -49,3 +49,9 @@ http_file(
         ]
     ],
 )
+
+buildifier_repositories = use_extension("//tools:buildifier_repositories.bzl", "buildifier_repositories")
+use_repo(buildifier_repositories, "buildifier-darwin-amd64")
+use_repo(buildifier_repositories, "buildifier-darwin-arm64")
+use_repo(buildifier_repositories, "buildifier-linux-amd64")
+use_repo(buildifier_repositories, "buildifier-linux-arm64")

tools/BUILD.bazel

@@ -84,8 +84,9 @@ bazel_lint_test(
     name = "bazel_lint_test",
     srcs = [
         "BUILD.bazel",
+        "buildifier_repositories.bzl",
+        "buildifier_version.bzl",
         "defs.bzl",
-        "workspace_versions.bzl",
     ],
 )
 

tools/buildifier_repositories.bzl

@@ -0,0 +1,21 @@
+load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_file")
+load("//tools:buildifier_version.bzl", "BUILDIFIER_VERSION")
+
+def _impl(_ctx):
+    releases = "https://github.com/bazelbuild/buildtools/releases"
+    version = BUILDIFIER_VERSION["version"]
+    for name, sha256 in BUILDIFIER_VERSION["binaries"].items():
+        http_file(
+            name = name,
+            executable = True,
+            sha256 = sha256,
+            url = "{releases}/download/v{version}/{name}".format(
+                releases = releases,
+                version = version,
+                name = name,
+            ),
+        )
+
+buildifier_repositories = module_extension(
+    implementation = _impl,
+)

tools/buildifier_version.bzl

@@ -0,0 +1,9 @@
+BUILDIFIER_VERSION = {
+    "version": "7.3.1",
+    "binaries": {
+        "buildifier-darwin-amd64": "375f823103d01620aaec20a0c29c6cbca99f4fd0725ae30b93655c6704f44d71",
+        "buildifier-darwin-arm64": "5a6afc6ac7a09f5455ba0b89bd99d5ae23b4174dc5dc9d6c0ed5ce8caac3f813",
+        "buildifier-linux-amd64": "5474cc5128a74e806783d54081f581662c4be8ae65022f557e9281ed5dc88009",
+        "buildifier-linux-arm64": "0bf86c4bfffaf4f08eed77bde5b2082e4ae5039a11e2e8b03984c173c34a561c",
+    },
+}

tools/upgrade.sh

@@ -13,7 +13,7 @@ me=$(python3 -c 'import os; print(os.path.realpath("'"$0"'"))')
 cd $(dirname "$me")/..
 
 python3 -B ./tools/upgrade_helper.py
-./bazel run //tools:buildifier tools/workspace_versions.bzl
+./bazel run //tools:buildifier tools/buildifier_version.bzl
 
 ./bazel run //:requirements.update -- --upgrade
 ./bazel run //examples:requirements.update -- --upgrade

tools/upgrade_helper.py

@@ -34,36 +34,22 @@ def _write_bazelisk_version(new, sha256):
         f.write(new_content)
 
 
-def _get_current_bazel_version() -> str:
-    """Parses ``.bazelversion`` for the old version of bazel."""
-    with open(".bazelversion", encoding="utf-8") as f:
-        lines = f.read().splitlines()
-    (line,) = lines
-    return line.strip()
-
-
-def _write_bazel_version(new):
-    """Overwrites ``.bazelversion`` with the new version of bazel."""
-    with open(".bazelversion", "w", encoding="utf-8") as f:
-        f.write(f"{new}\n")
-
-
-def _get_current_workspace_versions():
-    """Parses ``workspace_versions.bzl`` for the old versions."""
-    with open("tools/workspace_versions.bzl", encoding="utf-8") as f:
+def _get_current_buildifier_version():
+    """Parses ``buildifier_version.bzl`` for the old version."""
+    with open("tools/buildifier_version.bzl", encoding="utf-8") as f:
         content = f.read()
-    prefix = "WORKSPACE_VERSIONS = "
+    prefix = "BUILDIFIER_VERSION = "
     assert content.startswith(prefix)
     return ast.literal_eval(content.removeprefix(prefix))
 
 
-def _write_workspace_versions(new):
-    """Overwrites ``workspace_versions.bzl`` with the new versions.
+def _write_buildifier_version(new):
+    """Overwrites ``buildifier_version.bzl`` with the new version.
     We assume that tools/update.sh will run buildifier formatting afterwards.
     """
-    prefix = "WORKSPACE_VERSIONS = "
+    prefix = "BUILDIFIER_VERSION = "
     content = prefix + pformat(new, width=1, sort_dicts=False)
-    with open("tools/workspace_versions.bzl", "w", encoding="utf-8") as f:
+    with open("tools/buildifier_version.bzl", "w", encoding="utf-8") as f:
         f.write(content)
 
 
@@ -111,39 +97,27 @@ def _upgrade_bazelisk():
     _write_bazelisk_version(new, sha256)
 
 
-def _upgrade_bazel():
-    """Upgrades bazel to its latest version (if necessary)."""
-    old = _get_current_bazel_version()
-    new = _find_latest_github_release("bazelbuild/bazel")
-    if new == old:
-        print(f"bazel is already at the latest version {new}")
-        return
-    print(f"bazel will be upgraded to version {new}")
-    _write_bazel_version(new)
-
-
 def _upgrade_buildifier():
     """Upgrades buildifier to its latest version (if necessary)."""
-    workspace_versions = _get_current_workspace_versions()
-    old = workspace_versions["buildifier"]["version"]
+    buildifier_version = _get_current_buildifier_version()
+    old = buildifier_version["version"]
     new = _find_latest_github_release("bazelbuild/buildtools")
     if new == old:
         print(f"buildifier is already at the latest version {new}")
         return
     print(f"buildifier will be upgraded to version {new}")
-    workspace_versions["buildifier"]["version"] = new
-    names = list(workspace_versions["buildifier"]["binaries"].keys())
+    buildifier_version["version"] = new
+    names = list(buildifier_version["binaries"].keys())
     releases = "https://github.com/bazelbuild/buildtools/releases"
     for name in names:
-        workspace_versions["buildifier"]["binaries"][name] = _get_url_checksum(
+        buildifier_version["binaries"][name] = _get_url_checksum(
             f"{releases}/download/v{new}/{name}"
         )
-    _write_workspace_versions(workspace_versions)
+    _write_buildifier_version(buildifier_version)
 
 
 def _main():
     _upgrade_bazelisk()
-    _upgrade_bazel()
     _upgrade_buildifier()