Allow parallel execution

src/ablog/__init__.py

@@ -24,6 +24,7 @@
     process_postlist,
     process_posts,
     purge_posts,
+    merge_posts,
 )
 from .version import version as __version__
 
@@ -150,6 +151,7 @@ def setup(app):
     app.connect("builder-inited", builder_inited)
     app.connect("doctree-read", process_posts)
     app.connect("env-purge-doc", purge_posts)
+    app.connect("env-merge-info", merge_posts)
     app.connect("doctree-resolved", process_postlist)
     app.connect("missing-reference", missing_reference)
     app.connect("html-collect-pages", generate_archive_pages)
@@ -167,6 +169,6 @@ def setup(app):
     app.add_message_catalog(MESSAGE_CATALOG_NAME, locale_dir)
     return {
         "version": __version__,
-        "parallel_read_safe": False,
+        "parallel_read_safe": True,
         "parallel_write_safe": True,
     }

src/ablog/post.py

@@ -25,6 +25,7 @@
     "PostListDirective",
     "CheckFrontMatter",
     "purge_posts",
+    "merge_posts",
     "process_posts",
     "process_postlist",
     "generate_archive_pages",
@@ -220,6 +221,22 @@ def purge_posts(app, env, docname):
     env.domains["std"].data["anonlabels"].pop(filename, None)
 
 
+def merge_posts(app, env, docnames, other):
+    """
+    Merge post data from a worker environment into the main environment
+    during parallel reading.
+    """
+    if hasattr(other, "ablog_posts"):
+        if not hasattr(env, "ablog_posts"):
+            env.ablog_posts = {}
+        # post doctrees reference the worker env via settings.env, which
+        # would end up in environment.pickle once per worker
+        for posts in other.ablog_posts.values():
+            for post in posts:
+                post["doctree"].document.settings.env = env
+        env.ablog_posts.update(other.ablog_posts)
+
+
 def _update_post_node(node, options, arguments):
     """
     Extract metadata from options and populate a post node.

src/ablog/tests/test_parallel.py

@@ -0,0 +1,16 @@
+import pytest
+
+
+@pytest.mark.sphinx("html", testroot="parallel", parallel=2)  # using roots/test-parallel
+def test_parallel_read(app, status, warning):
+    app.build()
+    assert app.statuscode == 0
+
+    html = (app.outdir / "postlist.html").read_text(encoding="utf-8")
+    for i in range(1, 5):
+        assert f"post {i}" in html
+
+    # merged posts must not keep the worker's env alive
+    for posts in app.env.ablog_posts.values():
+        for post in posts:
+            assert post["doctree"].document.settings.env is app.env