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[core] Lazy-load zeroconf/writer/yaml_util in __main__

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Every \`esphome\` CLI invocation pays the cost of whatever \`esphome/__main__.py\`
imports at module scope before the requested command even runs. This
moves three heavy imports into the functions that actually use them:

- \`esphome.zeroconf\` (discover_mdns_devices): only needed for the
  name_add_mac_suffix OTA discovery path.
- \`esphome.writer\`: only needed by compile/clean paths.
- \`esphome.yaml_util\`: only needed by codegen, config dump, and rename.

Local measurement drops from ~75ms to ~47ms (-37%) for a cold
\`python -c 'import esphome.__main__'\`. The zeroconf chain alone accounts
for most of the gain — the case that motivated the CI budget check.

Also adds a module-level note explaining the intent so future PRs don't
innocently promote these back to the top.

Retargets four test patches from \`esphome.__main__.discover_mdns_devices\`
to \`esphome.zeroconf.discover_mdns_devices\` now that the symbol is only
bound inside the function that calls it.
This commit is contained in:
J. Nick Koston
2026-04-23 14:47:10 -05:00
parent 99c80b7dfa
commit fa055b9e49
2 changed files with 27 additions and 6 deletions
Download Patch File Download Diff File Expand all files Collapse all files
tests/unit_tests/test_main.py
+4 -4
View File
@@ -2605,7 +2605,7 @@ def test_choose_upload_log_host_discovers_mac_suffix_devices(tmp_path: Path) ->
}
with (
patch(
"esphome.__main__.discover_mdns_devices", return_value=discovered
"esphome.zeroconf.discover_mdns_devices", return_value=discovered
) as mock_discover,
patch(
"esphome.__main__.choose_prompt", return_value="mydevice-abc123.local"
@@ -2653,7 +2653,7 @@ def test_choose_upload_log_host_mac_suffix_no_devices_found(
)
with (
patch("esphome.__main__.discover_mdns_devices", return_value={}),
patch("esphome.zeroconf.discover_mdns_devices", return_value={}),
caplog.at_level(logging.WARNING, logger="esphome.__main__"),
pytest.raises(EsphomeError),
):
@@ -2686,7 +2686,7 @@ def test_choose_upload_log_host_default_ota_discovers_mac_suffix(
"mydevice-def456.local": ["10.0.0.2"],
}
with patch(
"esphome.__main__.discover_mdns_devices", return_value=discovered
"esphome.zeroconf.discover_mdns_devices", return_value=discovered
) as mock_discover:
result = choose_upload_log_host(
default="OTA",
@@ -2715,7 +2715,7 @@ def test_choose_upload_log_host_default_ota_no_suffix_discovery(
name="mydevice",
)
with patch("esphome.__main__.discover_mdns_devices") as mock_discover:
with patch("esphome.zeroconf.discover_mdns_devices") as mock_discover:
result = choose_upload_log_host(
default="OTA",
check_default=None,