Unlink a damaged build_info.json so regeneration completes, and log the replacement

The widened except left non-UTF-8 damage half-fixed: the staleness branch
fired, but write_file_if_changed then re-read the damaged file and raised
EsphomeError. Unlinking in the handler makes the recovery self-sufficient,
and the warning makes a repeatedly unreadable file visible instead of
silently costing a rebuild each run. The non-UTF-8 case now runs end to
end as a third row of the parametrized damage test, replacing the stubbed
decision-only test.

esphome/writer.py

@@ -1,3 +1,4 @@
+from contextlib import suppress
 import importlib
 import json
 import logging
@@ -343,8 +344,12 @@ def copy_src_tree():
             ):
                 # Non-object JSON is stale like every other damage case
                 sources_changed = True
-        except (ValueError, OSError):
-            # ValueError covers both JSONDecodeError and UnicodeDecodeError
+        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)
             sources_changed = True
 
     # Write build_info header and JSON metadata

tests/unit_tests/test_writer.py

@@ -2118,8 +2118,8 @@ def test_copy_src_tree_detects_version_change(
 
 @pytest.mark.parametrize(
     "damage",
-    (b"invalid json {{{", b"[]"),
-    ids=("invalid-json", "non-object"),
+    (b"invalid json {{{", b"[]", b'\xff{"config_hash": 1}'),
+    ids=("invalid-json", "non-object", "non-utf8"),
 )
 @patch("esphome.writer.CORE")
 @patch("esphome.writer.iter_components")
@@ -2143,35 +2143,6 @@ def test_copy_src_tree_regenerates_damaged_build_info(
     assert new_json["config_hash"] == 0xDEADBEEF
 
 
-@patch("esphome.writer.write_file_if_changed", return_value=False)
-@patch("esphome.writer.CORE")
-@patch("esphome.writer.iter_components")
-@patch("esphome.writer.walk_files")
-def test_copy_src_tree_non_utf8_build_info_reads_as_stale(
-    mock_walk_files: MagicMock,
-    mock_iter_components: MagicMock,
-    mock_core: MagicMock,
-    mock_write: MagicMock,
-    tmp_path: Path,
-) -> None:
-    """Non-UTF-8 build_info.json fires the staleness branch instead of raising.
-
-    Writes are stubbed (returning False, so nothing else can set
-    sources_changed): regenerating over the damaged file needs
-    write_file_if_changed's own recovery, which lands separately.
-    """
-    build_info_json_path = _setup_build_info_mocks(
-        mock_core, mock_iter_components, mock_walk_files, tmp_path
-    )
-    core_path = tmp_path / "src" / "esphome" / "core"
-    (core_path / "build_info_data.h").write_text("// old")
-    (core_path / "build_info_data.cpp").write_text("// old")
-    build_info_json_path.write_bytes(b'\xff{"config_hash": 1}')
-    _run_copy_src_tree()
-    written = [call.args[0] for call in mock_write.call_args_list]
-    assert build_info_json_path in written
-
-
 @patch("esphome.writer.CORE")
 @patch("esphome.writer.iter_components")
 @patch("esphome.writer.walk_files")