Script a list of proposals in proposals/README.md (#92)

Per request from chandlerc, to make it easier to skim proposal titles outside the website.

Also fix the title of markdown-toc.

.pre-commit-config.yaml

@@ -24,13 +24,21 @@ repos:
   - repo: local
     hooks:
       - id: markdown-toc
-        name: markdown-toc
+        name: Update table of contents
         description: Runs https://github.com/jonschlinkert/markdown-toc
         entry: src/scripts/pre-commit-toc.js
         language: node
         additional_dependencies: [markdown-toc]
         files: .*\.md$
         exclude: ^src/jekyll/theme/
+      - id: proposal-list
+        name: Update list of proposals
+        description: Updates the list of proposals in proposals/README.md
+        entry: src/scripts/pre-commit-proposal-list.py
+        language: python
+        language_version: python3
+        files: ^proposals/(README|p.*)\.md$
+        pass_filenames: false
   # Formatters should be run late so that they can re-format any prior changes.
   - repo: https://github.com/psf/black
     rev: stable

proposals/README.md

@@ -17,3 +17,15 @@ request:
 - `p####-decision.md` documents the decision and rationale.
 - `p####` may be present as an optional subdirectory for related files (e.g.,
   images).
+
+## Proposal list
+
+<!-- proposals -->
+<!-- This list is updated by src/scripts/pre-commit-proposal-list.py. -->
+
+- [0044 - Proposal tracking](p0044.md)
+  - [Decision](p0044-decision.md)
+- [0074 - Change comment/decision timelines in proposal process](p0074.md)
+  - [Decision](p0074-decision.md)
+
+<!-- endproposals -->

src/scripts/pre-commit-proposal-list.py

@@ -0,0 +1,71 @@
+#!/usr/bin/env python3
+
+"""Updates the list of proposals in proposals/README.md."""
+
+__copyright__ = """
+Part of the Carbon Language project, under the Apache License v2.0 with LLVM
+Exceptions. See /LICENSE for license information.
+SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+"""
+
+import os
+import re
+import sys
+
+if __name__ == "__main__":
+    # Read the proposal dir relative to this script.
+    proposal_dir = os.path.realpath(
+        os.path.join(os.path.dirname(sys.argv[0]), "../../proposals/")
+    )
+    print(proposal_dir)
+
+    # Identify proposal titles in the file list.
+    proposals = [
+        "<!-- This list is updated by src/scripts/pre-commit-proposal-list.py. "
+        "-->",
+        "",
+    ]
+    error = False
+    for file in sorted(os.listdir(proposal_dir)):
+        file_match = re.match(r"^p([0-9]{4})\.md$", file)
+        if not file_match:
+            continue
+        with open(os.path.join(proposal_dir, file)) as f:
+            content = f.read()
+        title = content.split("\n")[0]
+        title_match = re.match(r"^# (.*)$", title)
+        if not title_match:
+            print("ERROR: %s doesn't have a title on the first line." % file)
+            error = True
+        proposals.append(
+            "- [%s - %s](%s)" % (file_match[1], title_match[1], file)
+        )
+        decision_file = "p%s-decision.md" % file_match[1]
+        if os.path.exists(os.path.join(proposal_dir, decision_file)):
+            proposals.append("  - [Decision](%s)" % decision_file)
+    # We print batched errors for usability, but still need to exit with
+    # failure.
+    if error:
+        sys.exit(1)
+
+    # Replace the README content if needed.
+    readme_path = os.path.join(proposal_dir, "README.md")
+    with open(readme_path) as f:
+        old_content = f.read()
+    proposals_re = re.compile(
+        r"(.*<!-- proposals -->)(?:.*)(<!-- endproposals -->)",
+        re.DOTALL | re.MULTILINE,
+    )
+    if not proposals_re.match(old_content):
+        print(
+            "ERROR: proposals/README.md is missing the <!-- proposals --> ... "
+            "<!-- endproposals --> marker."
+        )
+        sys.exit(1)
+    new_content = proposals_re.sub(
+        r"\1\n%s\n\n\2" % "\n".join(proposals), old_content
+    )
+    if old_content != new_content:
+        print("Updating proposals/README.md")
+        with open(readme_path, "w") as f:
+            f.write(new_content)