Rebuild quietly on an absent build_info.json, log a failed unlink

FileNotFoundError is an OSError, so a merely missing file logged a
'damaged' warning; it now takes its own silent-stale branch, which also
makes missing_ok on the unlink unnecessary. An unlink failure on a truly
damaged file is logged by cause, since the kept copy makes the later
write fail with a misattributed error.

esphome/writer.py

@@ -1,4 +1,3 @@
-from contextlib import suppress
 import importlib
 import json
 import logging
@@ -344,12 +343,21 @@ def copy_src_tree():
             ):
                 # Non-object JSON is stale like every other damage case
                 sources_changed = True
+        except FileNotFoundError:
+            # An absent build_info.json is stale, not damaged; rebuild quietly
+            sources_changed = True
         except (ValueError, OSError) as err:
             # ValueError covers both JSONDecodeError and UnicodeDecodeError;
             # unlink so the regenerating write never re-reads the damage
             _LOGGER.warning("Replacing damaged build_info.json: %s", err)
-            with suppress(OSError):
-                build_info_json_path.unlink(missing_ok=True)
+            try:
+                build_info_json_path.unlink()
+            except OSError as unlink_err:
+                # The later write re-reads the file, so a kept damaged copy
+                # fails again with a misattributed error; name the real cause
+                _LOGGER.warning(
+                    "Could not remove damaged build_info.json: %s", unlink_err
+                )
             sources_changed = True
 
     # Write build_info header and JSON metadata

tests/unit_tests/test_writer.py

@@ -2143,6 +2143,56 @@ def test_copy_src_tree_regenerates_damaged_build_info(
     assert new_json["config_hash"] == 0xDEADBEEF
 
 
+@patch("esphome.writer.CORE")
+@patch("esphome.writer.iter_components")
+@patch("esphome.writer.walk_files")
+def test_copy_src_tree_missing_build_info_rebuilds_quietly(
+    mock_walk_files: MagicMock,
+    mock_iter_components: MagicMock,
+    mock_core: MagicMock,
+    tmp_path: Path,
+    caplog: pytest.LogCaptureFixture,
+) -> None:
+    """An absent build_info.json regenerates without claiming damage."""
+    build_info_json_path = _setup_build_info_mocks(
+        mock_core, mock_iter_components, mock_walk_files, tmp_path
+    )
+    _run_copy_src_tree()
+    build_info_json_path.unlink()
+    _run_copy_src_tree()
+    assert json.loads(build_info_json_path.read_text())["config_hash"] == 0xDEADBEEF
+    assert "damaged" not in caplog.text
+
+
+@patch("esphome.writer.CORE")
+@patch("esphome.writer.iter_components")
+@patch("esphome.writer.walk_files")
+def test_copy_src_tree_unremovable_damaged_build_info_is_logged(
+    mock_walk_files: MagicMock,
+    mock_iter_components: MagicMock,
+    mock_core: MagicMock,
+    tmp_path: Path,
+    caplog: pytest.LogCaptureFixture,
+) -> None:
+    """A failed unlink of the damaged file names the real cause."""
+    build_info_json_path = _setup_build_info_mocks(
+        mock_core, mock_iter_components, mock_walk_files, tmp_path
+    )
+    _run_copy_src_tree()
+    build_info_json_path.write_text("invalid json {{{")
+    real_unlink = Path.unlink
+
+    def fail_on_build_info(self: Path, missing_ok: bool = False) -> None:
+        if self.name == "build_info.json":
+            raise OSError("simulated EACCES")
+        real_unlink(self, missing_ok=missing_ok)
+
+    with patch.object(Path, "unlink", fail_on_build_info):
+        _run_copy_src_tree()
+    assert "Could not remove damaged build_info.json" in caplog.text
+    assert json.loads(build_info_json_path.read_text())["config_hash"] == 0xDEADBEEF
+
+
 @patch("esphome.writer.CORE")
 @patch("esphome.writer.iter_components")
 @patch("esphome.writer.walk_files")