Use `is`/`is not` for same-enum identity comparisons (source) by justanotherariel · Pull Request #171591 · home-assistant/core

justanotherariel · 2026-05-20T14:47:58Z

Proposed change

Mechanical codemod that replaces == with is (and != with is not)
on every line where both operands statically resolve to the same enum
class — as identified by mypy_plugins.enum_identity_compare from
#171551.

This PR covers homeassistant/ source files only (156 files,
289 sites). The corresponding tests-side codemod is in #171689.

# Before:
if self.state == ConfigEntryState.LOADED:  # both sides are ConfigEntryState
# After:
if self.state is ConfigEntryState.LOADED:

Scope is intentionally narrow:

Plain enum.Enum subclasses — 100% safe, because Enum.__eq__
is identity-based: == and is give the same result.
homeassistant.data_entry_flow.FlowResultType — the only
StrEnum on a curated allowlist, because HA's framework controls
every value-assigning callsite (async_show_form, async_create_entry,
etc. all set it to the enum instance).

What is NOT changed:

Other StrEnum/IntEnum/ReprEnum subclasses (HVACMode,
HTTPStatus, Platform, EntityCategory, ...). Their __eq__
delegates to str/int equality, and callers routinely pass the
underlying primitive (which is the whole reason those base classes
exist). Replacing == with is there would silently break behavior.
Flag/IntFlag — bitwise == is idiomatic.

Type of change

Dependency upgrade
Bugfix (non-breaking change which fixes an issue)
New integration (thank you!)
New feature (which adds functionality to an existing integration)
Deprecation (breaking change to happen in the future)
Breaking change (fix/feature causing existing functionality to break)
Code quality improvements to existing code or addition of tests

Additional information

This PR fixes or closes issue: fixes #
This PR is related to issue: Add mypy plugin: flag ==/!= between same-enum operands #171551 (plugin), Use is/is not for same-enum identity comparisons (tests) #171689 (tests-side codemod)
Link to documentation pull request:
Link to developer documentation pull request:
Link to frontend pull request:

The codemod is independent of #171551 and of the tests-side codemod.
All three can land in any order; CI on the plugin will be fully clean
only once both codemod halves land.

Checklist

I understand the code I am submitting and can explain how it works.
The code change is tested and works locally.
Local tests pass. Your PR cannot be merged unless tests pass
There is no commented out code in this PR.
I have followed the development checklist
I have followed the perfect PR recommendations
The code has been formatted using Ruff (ruff format homeassistant tests)
Tests have been added to verify that the new code works.
Any generated code has been carefully reviewed for correctness and compliance with project standards.

If user exposed functionality or configuration variables are added/changed:

Documentation added/updated for www.home-assistant.io

If the code communicates with devices, web services, or third-party tools:

The manifest file has all fields filled out correctly.
Updated and included derived files by running: python3 -m script.hassfest.
New or updated dependencies have been added to requirements_all.txt.
Updated by running python3 -m script.gen_requirements_all.
For the updated dependencies a diff between library versions and ideally a link to the changelog/release notes is added to the PR description.

To help with the load of incoming pull requests:

I have reviewed two other open pull requests in this repository.

home-assistant

There is a merge conflict.

home-assistant · 2026-05-20T14:48:08Z

Please take a look at the requested changes, and use the Ready for review button when you are done, thanks 👍

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thecode · 2026-05-20T14:55:44Z

While not mandatory I suggest splitting this into few smaller PR since it changes 765 files which make it impossible to review and very easily create a merge conflict.

justanotherariel · 2026-05-20T14:57:14Z

Yea, I think I agree 😅

epenet · 2026-05-21T07:38:49Z

Considering the number of CI failures with the patch applied, it suggests a definite regression is going on.

I don't know if the issue is with the patch, or if the issue comes from the mypy plugin, but I suggest to avoid changing "tests" at the same time as "homeassistant"

justanotherariel · 2026-05-21T07:56:06Z

it suggests a definite regression is going on

Yes, and I already found the issue. Modified the plugin. You're right though - I will create 2 Prs and split out homeassistant and test changes!

Copilot

Pull request overview

Copilot reviewed 251 out of 251 changed files in this pull request and generated 1 comment.

Mechanical codemod that replaces `==` with `is` (and `!=` with `is not`) on every line where both operands statically resolve to the same enum class — as identified by `mypy_plugins.enum_identity_compare` from home-assistant#171551. This commit covers `homeassistant/` only (156 files, 289 sites). The companion tests-side change is in home-assistant#171689. Scope is intentionally narrow: - Plain `enum.Enum` subclasses: `Enum.__eq__` is identity-based, so `==` and `is` are mathematically equivalent. - `homeassistant.data_entry_flow.FlowResultType`: explicitly allowlisted StrEnum where HA's framework normalizes every consumer-facing result to the enum instance. NOT changed: other StrEnum/IntEnum/ReprEnum subclasses (their `__eq__` delegates to str/int equality and accepts raw primitives at runtime), and Flag/IntFlag (bitwise `==` is idiomatic). `homeassistant/data_entry_flow.py:497` is the one exception left as `!=` (with a noqa) because it runs before the legacy-string normalization shim a few lines below. Verified by re-running the mypy plugin against the codemodded source: zero remaining violations on this side.

The original line had two `==` comparisons on it: an enum compare (entry.state == ConfigEntryState.LOADED) and an unrelated str-vs-str compare (entry.domain == DOMAIN). The codemod's line-level replacement swapped both. Restoring the str compare to `==` since string interning is not guaranteed and the mypy plugin only flagged the enum site. Resolves Copilot review comment on home-assistant#171591.

Copilot

Pull request overview

Copilot reviewed 156 out of 156 changed files in this pull request and generated 1 comment.

…ant#171699) The IntentResponseType.ERROR identity swap in DefaultAgent.async_handle_intents is being handled in its own PR (home-assistant#171699) alongside an adjustment to a brittle mock_calls assertion that broke when the operator changed. Reverting just that one site here so the two PRs don't conflict on the same line.

Copilot

Pull request overview

Copilot reviewed 156 out of 156 changed files in this pull request and generated no new comments.

Re-running the plugin (now handling LiteralType and UnionType, per home-assistant#171551) flagged 38 additional same-enum compare sites in homeassistant/ — typically the elif arm of an is/== chain (where mypy narrows the operand to a union of literals) and Literal[E.X]-annotated parameters. Pure ==/is and !=/is-not swaps, no other changes.

Copilot AI review requested due to automatic review settings May 20, 2026 14:48

justanotherariel requested a review from a team as a code owner May 20, 2026 14:48

home-assistant Bot previously requested changes May 20, 2026

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justanotherariel requested a review from dmulcahey as a code owner May 20, 2026 14:48

home-assistant Bot added cla-signed code-quality labels May 20, 2026

justanotherariel requested a review from Adminiuga as a code owner May 20, 2026 14:48

home-assistant Bot added the core label May 20, 2026

justanotherariel requested review from a team, Ernst79, Jc2k, TheJulianJES, abmantis, bdraco, frenck, gjohansson-ST, joostlek, puddly, rytilahti, starkillerOG, synesthesiam and syssi as code owners May 20, 2026 14:48

home-assistant Bot marked this pull request as draft May 20, 2026 14:48

justanotherariel requested a review from thecode as a code owner May 20, 2026 14:48

justanotherariel requested review from MartinHjelmare, StevenLooman, chemelli74, dgomes and raman325 as code owners May 20, 2026 14:48

justanotherariel requested review from Swamp-Ig, andrewsayre, cgarwood, edenhaus, jesserockz, kbx81, marcelveldt, mdegat01, pvizeli, rohankapoorcom and zxdavb as code owners May 20, 2026 14:48

justanotherariel mentioned this pull request May 20, 2026

Use is/is not for same-enum identity comparisons (2/3) #171596

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This was referenced May 20, 2026

Use is/is not for same-enum identity comparisons (3/3) #171597

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Add mypy plugin: flag ==/!= between same-enum operands #171551

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Comment thread homeassistant/components/octoprint/__init__.py

justanotherariel mentioned this pull request May 21, 2026

Use is/is not for same-enum identity comparisons (tests) #171689

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justanotherariel added 2 commits May 21, 2026 11:37

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Comment thread homeassistant/data_entry_flow.py

justanotherariel mentioned this pull request May 21, 2026

Use is for IntentResponseType identity check in conversation #171699

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Comment thread homeassistant/components/arcam_fmj/media_player.py Outdated

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Use `is`/`is not` for same-enum identity comparisons (source)#171591

Use `is`/`is not` for same-enum identity comparisons (source)#171591
joostlek merged 4 commits into
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justanotherariel:automation-enum-is-codemod

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