Refactor BuildInfo and move to a new module

sphinx/builders/_epub_base.py

@@ -15,7 +15,8 @@
 from docutils.utils import smartquotes
 
 from sphinx import addnodes
-from sphinx.builders.html import BuildInfo, StandaloneHTMLBuilder
+from sphinx.builders.html import StandaloneHTMLBuilder
+from sphinx.builders.html._build_info import BuildInfo
 from sphinx.locale import __
 from sphinx.util import logging
 from sphinx.util.display import status_iterator

sphinx/builders/html/__init__.py

@@ -3,17 +3,16 @@
 from __future__ import annotations
 
 import contextlib
-import hashlib
 import html
 import os
 import posixpath
 import re
+import shutil
 import sys
-import types
 import warnings
 from os import path
 from pathlib import Path
-from typing import IO, TYPE_CHECKING, Any
+from typing import TYPE_CHECKING, Any
 from urllib.parse import quote
 
 import docutils.readers.doctree
@@ -31,6 +30,7 @@
     _file_checksum,
     _JavaScript,
 )
+from sphinx.builders.html._build_info import BuildInfo
 from sphinx.config import ENUM, Config
 from sphinx.deprecation import _deprecation_warning
 from sphinx.domains import Domain, Index, IndexEntry
@@ -63,16 +63,14 @@
 from sphinx.writers.html5 import HTML5Translator
 
 if TYPE_CHECKING:
-    from collections.abc import Iterable, Iterator, Set
+    from collections.abc import Iterable, Iterator
     from typing import TypeAlias
 
     from docutils.nodes import Node
     from docutils.readers import Reader
 
     from sphinx.application import Sphinx
-    from sphinx.config import _ConfigRebuild
     from sphinx.environment import BuildEnvironment
-    from sphinx.util.tags import Tags
     from sphinx.util.typing import ExtensionMetadata
 
 #: the filename for the inventory of objects
@@ -93,23 +91,6 @@
 ]
 
 
-def _stable_hash(obj: Any) -> str:
-    """Return a stable hash for a Python data structure.
-
-    We can't just use the md5 of str(obj) as the order of collections
-    may be random.
-    """
-    if isinstance(obj, dict):
-        obj = sorted(map(_stable_hash, obj.items()))
-    if isinstance(obj, list | tuple | set | frozenset):
-        obj = sorted(map(_stable_hash, obj))
-    elif isinstance(obj, type | types.FunctionType):
-        # The default repr() of functions includes the ID, which is not ideal.
-        # We use the fully qualified name instead.
-        obj = f'{obj.__module__}.{obj.__qualname__}'
-    return hashlib.md5(str(obj).encode(), usedforsecurity=False).hexdigest()
-
-
 def convert_locale_to_language_tag(locale: str | None) -> str | None:
     """Convert a locale string to a language tag (ex. en_US -> en-US).
 
@@ -121,57 +102,6 @@ def convert_locale_to_language_tag(locale: str | None) -> str | None:
         return None
 
 
-class BuildInfo:
-    """buildinfo file manipulator.
-
-    HTMLBuilder and its family are storing their own envdata to ``.buildinfo``.
-    This class is a manipulator for the file.
-    """
-
-    @classmethod
-    def load(cls: type[BuildInfo], f: IO[str]) -> BuildInfo:
-        try:
-            lines = f.readlines()
-            assert lines[0].rstrip() == '# Sphinx build info version 1'
-            assert lines[2].startswith('config: ')
-            assert lines[3].startswith('tags: ')
-
-            build_info = BuildInfo()
-            build_info.config_hash = lines[2].split()[1].strip()
-            build_info.tags_hash = lines[3].split()[1].strip()
-            return build_info
-        except Exception as exc:
-            raise ValueError(__('build info file is broken: %r') % exc) from exc
-
-    def __init__(
-        self,
-        config: Config | None = None,
-        tags: Tags | None = None,
-        config_categories: Set[_ConfigRebuild] = frozenset(),
-    ) -> None:
-        self.config_hash = ''
-        self.tags_hash = ''
-
-        if config:
-            values = {c.name: c.value for c in config.filter(config_categories)}
-            self.config_hash = _stable_hash(values)
-
-        if tags:
-            self.tags_hash = _stable_hash(sorted(tags))
-
-    def __eq__(self, other: BuildInfo) -> bool:  # type: ignore[override]
-        return (self.config_hash == other.config_hash and
-                self.tags_hash == other.tags_hash)
-
-    def dump(self, f: IO[str]) -> None:
-        f.write('# Sphinx build info version 1\n'
-                '# This file hashes the configuration used when building these files.'
-                ' When it is not found, a full rebuild will be done.\n'
-                'config: %s\n'
-                'tags: %s\n' %
-                (self.config_hash, self.tags_hash))
-
-
 class StandaloneHTMLBuilder(Builder):
     """
     Builds standalone HTML docs.
@@ -396,18 +326,28 @@ def math_renderer_name(self) -> str | None:
     def get_outdated_docs(self) -> Iterator[str]:
         build_info_fname = self.outdir / '.buildinfo'
         try:
-            with open(build_info_fname, encoding="utf-8") as fp:
-                buildinfo = BuildInfo.load(fp)
-
-            if self.build_info != buildinfo:
-                logger.debug('[build target] did not match: build_info ')
-                yield from self.env.found_docs
-                return
+            build_info = BuildInfo.load(build_info_fname)
         except ValueError as exc:
             logger.warning(__('Failed to read build info file: %r'), exc)
         except OSError:
             # ignore errors on reading
             pass
+        else:
+            if self.build_info != build_info:
+                # log the mismatch and backup the old build info
+                build_info_backup = build_info_fname.with_name('.buildinfo.bak')
+                try:
+                    shutil.move(build_info_fname, build_info_backup)
+                    self.build_info.dump(build_info_fname)
+                except OSError:
+                    pass  # ignore errors
+                else:
+                    # only log on success
+                    msg = __('build_info mismatch, copying .buildinfo to .buildinfo.bak')
+                    logger.info(bold(__('building [html]: ')) + msg)
+
+                yield from self.env.found_docs
+                return
 
         if self.templates:
             template_mtime = int(self.templates.newest_template_mtime() * 10**6)
@@ -943,8 +883,7 @@ def copy_extra_files(self) -> None:
 
     def write_buildinfo(self) -> None:
         try:
-            with open(path.join(self.outdir, '.buildinfo'), 'w', encoding="utf-8") as fp:
-                self.build_info.dump(fp)
+            self.build_info.dump(self.outdir / '.buildinfo')
         except OSError as exc:
             logger.warning(__('Failed to write build info file: %r'), exc)
 

sphinx/builders/html/_build_info.py

@@ -0,0 +1,94 @@
+"""Record metadata for the build process."""
+
+from __future__ import annotations
+
+import hashlib
+import types
+from typing import TYPE_CHECKING
+
+from sphinx.locale import __
+
+if TYPE_CHECKING:
+    from collections.abc import Set
+    from pathlib import Path
+    from typing import Any
+
+    from sphinx.config import Config, _ConfigRebuild
+    from sphinx.util.tags import Tags
+
+
+class BuildInfo:
+    """buildinfo file manipulator.
+
+    HTMLBuilder and its family are storing their own envdata to ``.buildinfo``.
+    This class is a manipulator for the file.
+    """
+
+    @classmethod
+    def load(cls: type[BuildInfo], filename: Path, /) -> BuildInfo:
+        content = filename.read_text(encoding="utf-8")
+        lines = content.splitlines()
+
+        version = lines[0].rstrip()
+        if version != '# Sphinx build info version 1':
+            msg = __('failed to read broken build info file (unknown version)')
+            raise ValueError(msg)
+
+        if not lines[2].startswith('config: '):
+            msg = __('failed to read broken build info file (missing config entry)')
+            raise ValueError(msg)
+        if not lines[3].startswith('tags: '):
+            msg = __('failed to read broken build info file (missing tags entry)')
+            raise ValueError(msg)
+
+        build_info = BuildInfo()
+        build_info.config_hash = lines[2].removeprefix('config: ').strip()
+        build_info.tags_hash = lines[3].removeprefix('tags: ').strip()
+        return build_info
+
+    def __init__(
+        self,
+        config: Config | None = None,
+        tags: Tags | None = None,
+        config_categories: Set[_ConfigRebuild] = frozenset(),
+    ) -> None:
+        self.config_hash = ''
+        self.tags_hash = ''
+
+        if config:
+            values = {c.name: c.value for c in config.filter(config_categories)}
+            self.config_hash = _stable_hash(values)
+
+        if tags:
+            self.tags_hash = _stable_hash(sorted(tags))
+
+    def __eq__(self, other: BuildInfo) -> bool:  # type: ignore[override]
+        return (self.config_hash == other.config_hash and
+                self.tags_hash == other.tags_hash)
+
+    def dump(self, filename: Path, /) -> None:
+        build_info = (
+            '# Sphinx build info version 1\n'
+            '# This file records the configuration used when building these files. '
+            'When it is not found, a full rebuild will be done.\n'
+            f'config: {self.config_hash}\n'
+            f'tags: {self.tags_hash}\n'
+        )
+        filename.write_text(build_info, encoding="utf-8")
+
+
+def _stable_hash(obj: Any) -> str:
+    """Return a stable hash for a Python data structure.
+
+    We can't just use the md5 of str(obj) as the order of collections
+    may be random.
+    """
+    if isinstance(obj, dict):
+        obj = sorted(map(_stable_hash, obj.items()))
+    if isinstance(obj, list | tuple | set | frozenset):
+        obj = sorted(map(_stable_hash, obj))
+    elif isinstance(obj, type | types.FunctionType):
+        # The default repr() of functions includes the ID, which is not ideal.
+        # We use the fully qualified name instead.
+        obj = f'{obj.__module__}.{obj.__qualname__}'
+    return hashlib.md5(str(obj).encode(), usedforsecurity=False).hexdigest()