[tests] Add CodSpeed benchmark for compiled-config cache fast path (#16402)

Co-authored-by: pre-commit-ci-lite[bot] <117423508+pre-commit-ci-lite[bot]@users.noreply.github.com>

tests/benchmarks/python/test_compiled_config_bench.py

@@ -0,0 +1,116 @@
+"""CodSpeed benchmarks for the validated-config cache fast path.
+
+PR #16381 added a cache that lets ``esphome upload`` / ``esphome logs``
+skip re-running the full config-validation pipeline. These benchmarks
+compare the cached path (``load_compiled_config``) against the slow
+path (``read_config``) on the same input.
+
+The fixture YAML is a modest bluetooth-proxy device. The two paths
+end up close on a config this small -- the win grows with config
+complexity (external components, large package trees, deeply nested
+schemas), where the slow path can be orders of magnitude slower than
+the cache load.
+
+Skipped when ``pytest-codspeed`` isn't installed so the regular
+unit-test suite keeps working unchanged.
+"""
+
+from __future__ import annotations
+
+from collections.abc import Callable
+from pathlib import Path
+import shutil
+from typing import Any
+
+import pytest
+
+from esphome.compiled_config import compiled_config_path, load_compiled_config
+from esphome.config import read_config
+from esphome.core import CORE
+from esphome.storage_json import ext_storage_path
+from esphome.writer import update_storage_json
+
+pytest.importorskip("pytest_codspeed")
+
+HERE = Path(__file__).parent
+FIXTURE_YAML = HERE / "fixtures" / "bluetooth_proxy_device.yaml"
+
+
+def _stage_yaml(tmp_path: Path) -> Path:
+    """Copy fixture YAML into a fresh tmp dir.
+
+    Each benchmark gets its own copy so the cache files (under
+    ``.esphome/storage/`` next to the YAML) don't bleed between cases.
+    """
+    target = tmp_path / FIXTURE_YAML.name
+    shutil.copy2(FIXTURE_YAML, target)
+    return target
+
+
+def _prime_cache(yaml_path: Path) -> None:
+    """Run full validation once and persist the cache + sidecar.
+
+    Mirrors ``esphome compile``: ``read_config`` populates ``CORE.config``,
+    then ``update_storage_json`` writes both the StorageJSON sidecar and
+    the ``.validated.yaml`` compiled-config cache.
+    """
+    CORE.config_path = yaml_path
+    config = read_config({}, skip_external_update=True)
+    assert config is not None, f"fixture YAML failed to validate: {yaml_path}"
+    CORE.config = config
+    update_storage_json()
+
+
+@pytest.fixture
+def staged_yaml(tmp_path: Path) -> Path:
+    """YAML copied into tmp_path; no cache files written yet."""
+    return _stage_yaml(tmp_path)
+
+
+@pytest.fixture
+def primed_yaml(staged_yaml: Path) -> Path:
+    """YAML plus a fresh cache + sidecar on disk."""
+    _prime_cache(staged_yaml)
+    assert compiled_config_path(staged_yaml.name).is_file()
+    assert ext_storage_path(staged_yaml.name).is_file()
+    return staged_yaml
+
+
+def _resetting_setup(
+    yaml_path: Path,
+    args: tuple[Any, ...],
+    kwargs: dict[str, Any],
+) -> Callable[[], tuple[tuple[Any, ...], dict[str, Any]]]:
+    """Build a per-iteration setup that resets CORE and re-pins config_path."""
+
+    def setup() -> tuple[tuple[Any, ...], dict[str, Any]]:
+        CORE.reset()
+        CORE.config_path = yaml_path
+        return args, kwargs
+
+    return setup
+
+
+def test_load_compiled_config_cached(primed_yaml: Path, benchmark) -> None:
+    """Fast path: deserialize the cached, already-validated config."""
+    benchmark.pedantic(
+        load_compiled_config,
+        setup=_resetting_setup(primed_yaml, (primed_yaml,), {}),
+        rounds=5,
+        iterations=1,
+    )
+
+
+def test_read_config_uncached(primed_yaml: Path, benchmark) -> None:
+    """Slow path: full validation pipeline (yaml load + schema + components).
+
+    Uses the same primed fixture as the cached path -- ``read_config``
+    ignores the cache file on disk, so the two benchmarks measure the
+    same input from two different code paths.
+    """
+    benchmark.pedantic(
+        read_config,
+        setup=_resetting_setup(primed_yaml, ({},), {"skip_external_update": True}),
+        rounds=3,
+        iterations=1,
+    )