Add diff_test asserting that docs are up-to-date (#321)

Based on Aspect's stardoc_with_diff_test; see https://github.com/aspect-build/bazel-lib/blob/main/docs/docs.md

.bazelci/presubmit.yml

@@ -46,6 +46,7 @@ tasks:
     # TODO(laszlocsomor): remove "--test_env=LOCALAPPDATA" after
     # https://github.com/bazelbuild/bazel/issues/7761 is fixed
     - "--test_env=LOCALAPPDATA"
+    - "--test_tag_filters=-no_windows"
 
   ubuntu1804_last_green:
     name: "Last Green Bazel"
@@ -93,5 +94,6 @@ tasks:
     # TODO(laszlocsomor): remove "--test_env=LOCALAPPDATA" after
     # https://github.com/bazelbuild/bazel/issues/7761 is fixed
     - "--test_env=LOCALAPPDATA"
+    - "--test_tag_filters=-no_windows"
 
 buildifier: latest

docs/BUILD

@@ -1,137 +1,104 @@
-load("@io_bazel_stardoc//stardoc:stardoc.bzl", "stardoc")
+load("//docs/private:stardoc_with_diff_test.bzl", "stardoc_with_diff_test", "update_docs")
 
 licenses(["notice"])
 
-# Note that due to a bug in Bazel 0.22.0, these targets cannot be built without
-# the --incompatible_remap_main_repo flag.
-stardoc(
-    name = "build_test_docs",
-    out = "build_test_doc_gen.md",
-    input = "//rules:build_test.bzl",
-    deps = ["//rules:build_test"],
+stardoc_with_diff_test(
+    bzl_library_target = "//rules:analysis_test",
+    out_label = "//docs:analysis_test_doc.md",
 )
 
-stardoc(
-    name = "analysis_test_docs",
-    out = "analysis_test_doc_gen.md",
-    input = "//rules:analysis_test.bzl",
+stardoc_with_diff_test(
+    bzl_library_target = "//rules:build_test",
+    out_label = "//docs:build_test_doc.md",
 )
 
-stardoc(
-    name = "collections_docs",
-    out = "collections_doc_gen.md",
-    input = "//lib:collections.bzl",
-    deps = ["//lib:collections"],
+stardoc_with_diff_test(
+    bzl_library_target = "//lib:collections",
+    out_label = "//docs:collections_doc.md",
 )
 
-stardoc(
-    name = "dicts_docs",
-    out = "dicts_doc_gen.md",
-    input = "//lib:dicts.bzl",
-    deps = ["//lib:dicts"],
+stardoc_with_diff_test(
+    bzl_library_target = "//rules:common_settings",
+    out_label = "//docs:common_settings_doc.md",
 )
 
-stardoc(
-    name = "partial_docs",
-    out = "partial_doc_gen.md",
-    input = "//lib:partial.bzl",
-    deps = ["//lib:partial"],
+stardoc_with_diff_test(
+    bzl_library_target = "//rules:copy_file",
+    out_label = "//docs:copy_file_doc.md",
 )
 
-stardoc(
-    name = "paths_docs",
-    out = "paths_doc_gen.md",
-    input = "//lib:paths.bzl",
-    deps = ["//lib:paths"],
+stardoc_with_diff_test(
+    bzl_library_target = "//lib:dicts",
+    out_label = "//docs:dicts_doc.md",
 )
 
-stardoc(
-    name = "selects_docs",
-    out = "selects_doc_gen.md",
-    input = "//lib:selects.bzl",
-    deps = ["//lib:selects"],
+stardoc_with_diff_test(
+    bzl_library_target = "//rules:diff_test",
+    out_label = "//docs:diff_test_doc.md",
 )
 
-stardoc(
-    name = "new_sets_docs",
-    out = "new_sets_doc_gen.md",
-    input = "//lib:new_sets.bzl",
-    deps = ["//lib:new_sets"],
+stardoc_with_diff_test(
+    bzl_library_target = "//rules:native_binary",
+    out_label = "//docs:native_binary_doc.md",
 )
 
-stardoc(
-    name = "shell_docs",
-    out = "shell_doc_gen.md",
-    input = "//lib:shell.bzl",
-    deps = ["//lib:shell"],
+stardoc_with_diff_test(
+    bzl_library_target = "//lib:new_sets",
+    out_label = "//docs:new_sets_doc.md",
 )
 
-stardoc(
-    name = "structs_docs",
-    out = "structs_doc_gen.md",
-    input = "//lib:structs.bzl",
-    deps = ["//lib:structs"],
+stardoc_with_diff_test(
+    bzl_library_target = "//lib:partial",
+    out_label = "//docs:partial_doc.md",
 )
 
-stardoc(
-    name = "types_docs",
-    out = "types_doc_gen.md",
-    input = "//lib:types.bzl",
-    deps = ["//lib:types"],
+stardoc_with_diff_test(
+    bzl_library_target = "//lib:paths",
+    out_label = "//docs:paths_doc.md",
 )
 
-stardoc(
-    name = "unittest_docs",
-    out = "unittest_doc_gen.md",
-    input = "//lib:unittest.bzl",
-    deps = ["//lib:unittest"],
+stardoc_with_diff_test(
+    bzl_library_target = "//rules:run_binary",
+    out_label = "//docs:run_binary_doc.md",
 )
 
-stardoc(
-    name = "versions_docs",
-    out = "versions_doc_gen.md",
-    input = "//lib:versions.bzl",
-    deps = ["//lib:versions"],
+stardoc_with_diff_test(
+    bzl_library_target = "//lib:selects",
+    out_label = "//docs:selects_doc.md",
 )
 
-stardoc(
-    name = "copy_file_docs",
-    out = "copy_file_doc_gen.md",
-    input = "//rules:copy_file.bzl",
-    deps = ["//rules:copy_file"],
+stardoc_with_diff_test(
+    bzl_library_target = "//lib:shell",
+    out_label = "//docs:shell_doc.md",
 )
 
-stardoc(
-    name = "write_file_docs",
-    out = "write_file_doc_gen.md",
-    input = "//rules:write_file.bzl",
-    deps = ["//rules:write_file"],
+stardoc_with_diff_test(
+    bzl_library_target = "//lib:structs",
+    out_label = "//docs:structs_doc.md",
 )
 
-stardoc(
-    name = "diff_test_docs",
-    out = "diff_test_doc_gen.md",
-    input = "//rules:diff_test.bzl",
-    deps = ["//rules:diff_test"],
+stardoc_with_diff_test(
+    bzl_library_target = "//lib:types",
+    out_label = "//docs:types_doc.md",
 )
 
-stardoc(
-    name = "native_binary_docs",
-    out = "native_binary_doc_gen.md",
-    input = "//rules:native_binary.bzl",
-    deps = ["//rules:native_binary"],
+stardoc_with_diff_test(
+    bzl_library_target = "//lib:unittest",
+    out_label = "//docs:unittest_doc.md",
 )
 
-stardoc(
-    name = "run_binary_docs",
-    out = "run_binary_doc_gen.md",
-    input = "//rules:run_binary.bzl",
-    deps = ["//rules:run_binary"],
+stardoc_with_diff_test(
+    bzl_library_target = "//lib:versions",
+    out_label = "//docs:versions_doc.md",
 )
 
-stardoc(
-    name = "common_settings_docs",
-    out = "common_settings_doc_gen.md",
-    input = "//rules:common_settings.bzl",
-    deps = ["//rules:common_settings"],
+stardoc_with_diff_test(
+    bzl_library_target = "//rules:write_file",
+    out_label = "//docs:write_file_doc.md",
+)
+
+# update_docs must be at the bottom of the BUILD file
+update_docs(
+    name = "update",
+    docs_folder = "docs",
 )

docs/private/BUILD

@@ -0,0 +1 @@
+# No targets in this package

docs/private/stardoc_with_diff_test.bzl

@@ -0,0 +1,96 @@
+"""Helpers for keeping stardoc documentation up-to-date.
+
+These are currently a private API in bazel-skylib.
+See discussion:
+https://github.com/bazelbuild/bazel-skylib/pull/321#issuecomment-1081166216
+
+If you need a similar feature, you can consider using a similar rule
+available from a third-party:
+https://github.com/aspect-build/bazel-lib/blob/main/docs/docs.md
+"""
+
+load("@io_bazel_stardoc//stardoc:stardoc.bzl", "stardoc")
+load("@bazel_skylib//rules:write_file.bzl", "write_file")
+load("@bazel_skylib//rules:diff_test.bzl", "diff_test")
+
+def stardoc_with_diff_test(
+        bzl_library_target,
+        out_label):
+    """Creates a stardoc target coupled with a `diff_test` for a given `bzl_library`.
+
+    This is helpful for minimizing boilerplate in repos wih lots of stardoc targets.
+
+    Args:
+        bzl_library_target: the label of the `bzl_library` target to generate documentation for
+        out_label: the label of the output MD file
+    """
+
+    out_file = out_label.replace("//", "").replace(":", "/")
+
+    # Generate MD from .bzl
+    stardoc(
+        name = out_file.replace("/", "_").replace(".md", "-docgen"),
+        out = out_file.replace(".md", "-docgen.md"),
+        input = bzl_library_target + ".bzl",
+        deps = [bzl_library_target],
+    )
+
+    # Ensure that the generated MD has been updated in the local source tree
+    diff_test(
+        name = out_file.replace("/", "_").replace(".md", "-difftest"),
+        failure_message = "Please run \"bazel run //docs:update\"",
+        # Source file
+        file1 = out_label,
+        # Output from stardoc rule above
+        file2 = out_file.replace(".md", "-docgen.md"),
+        tags = ["no_windows"],
+    )
+
+def update_docs(
+        name = "update",
+        docs_folder = "docs"):
+    """Creates a `sh_binary` target which copies over generated doc files to the local source tree.
+
+    This is to be used in tandem with `stardoc_with_diff_test()` to produce a convenient workflow
+    for generating, testing, and updating all doc files as follows:
+
+    ``` bash
+    bazel build //{docs_folder}/... && bazel test //{docs_folder}/... && bazel run //{docs_folder}:update
+    ```
+
+    eg.
+
+    ``` bash
+    bazel build //docs/... && bazel test //docs/... && bazel run //docs:update
+    ```
+
+    The `update_docs()` invocation must come after/below any `stardoc_with_diff_test()` invocations
+    in the BUILD file.
+
+    Args:
+        name: the name of the `sh_binary` target
+        docs_folder: the name of the folder containing the doc files in the local source tree
+    """
+    content = ["#!/usr/bin/env bash", "cd ${BUILD_WORKSPACE_DIRECTORY}"]
+    data = []
+    for r in native.existing_rules().values():
+        if r["kind"] == "stardoc":
+            doc_gen = r["out"]
+            if doc_gen.startswith(":"):
+                doc_gen = doc_gen[1:]
+            doc_dest = doc_gen.replace("-docgen.md", ".md")
+            data.append(doc_gen)
+            content.append("cp -fv bazel-bin/{0}/{1} {2}".format(docs_folder, doc_gen, doc_dest))
+
+    update_script = name + ".sh"
+    write_file(
+        name = "gen_" + name,
+        out = update_script,
+        content = content,
+    )
+
+    native.sh_binary(
+        name = name,
+        srcs = [update_script],
+        data = data,
+    )