ci: add public API snapshot check

[marandaneto]

💡 Motivation and Context

Add a generated public API snapshot check so CI can catch accidental changes to the SDK's exported public surface. The snapshot can be regenerated intentionally with make public_api_snapshot.

💚 How did you test it?

• uv run --extra dev python .github/scripts/check_public_api.py
• uv run --extra dev ruff check .github/scripts/check_public_api.py
• uv run --extra dev ruff format --check .github/scripts/check_public_api.py

📝 Checklist

• I reviewed the submitted code.
• I added tests to verify the changes.
• I updated the docs if needed.
• No breaking change or entry added to the changelog.

If releasing new changes

• Ran sampo add to generate a changeset file

[github-actions]

posthog-python Compliance Report

Date: 2026-06-15 15:57:21 UTC
Duration: 175636ms

✅ All Tests Passed!

45/45 tests passed

---

Capture Tests

✅ 29/29 tests passed

View Details

Test	Status	Duration
Format Validation.Event Has Required Fields	✅	517ms
Format Validation.Event Has Uuid	✅	1508ms
Format Validation.Event Has Lib Properties	✅	1507ms
Format Validation.Distinct Id Is String	✅	1508ms
Format Validation.Token Is Present	✅	1507ms
Format Validation.Custom Properties Preserved	✅	1507ms
Format Validation.Event Has Timestamp	✅	1507ms
Retry Behavior.Retries On 503	✅	9516ms
Retry Behavior.Does Not Retry On 400	✅	3510ms
Retry Behavior.Does Not Retry On 401	✅	3509ms
Retry Behavior.Respects Retry After Header	✅	9515ms
Retry Behavior.Implements Backoff	✅	23523ms
Retry Behavior.Retries On 500	✅	7513ms
Retry Behavior.Retries On 502	✅	7513ms
Retry Behavior.Retries On 504	✅	7510ms
Retry Behavior.Max Retries Respected	✅	23518ms
Deduplication.Generates Unique Uuids	✅	1011ms
Deduplication.Preserves Uuid On Retry	✅	7514ms
Deduplication.Preserves Uuid And Timestamp On Retry	✅	14515ms
Deduplication.Preserves Uuid And Timestamp On Batch Retry	✅	7517ms
Deduplication.No Duplicate Events In Batch	✅	1504ms
Deduplication.Different Events Have Different Uuids	✅	1508ms
Compression.Sends Gzip When Enabled	✅	1507ms
Batch Format.Uses Proper Batch Structure	✅	1508ms
Batch Format.Flush With No Events Sends Nothing	✅	1005ms
Batch Format.Multiple Events Batched Together	✅	1505ms
Error Handling.Does Not Retry On 403	✅	3510ms
Error Handling.Does Not Retry On 413	✅	3508ms
Error Handling.Retries On 408	✅	7515ms

Feature_Flags Tests

✅ 16/16 tests passed

View Details

Test	Status	Duration
Request Payload.Request With Person Properties Device Id	✅	1003ms
Request Payload.Flags Request Uses V2 Query Param	✅	1007ms
Request Payload.Flags Request Hits Flags Path Not Decide	✅	1007ms
Request Payload.Flags Request Omits Authorization Header	✅	1007ms
Request Payload.Token In Flags Body Matches Init	✅	1007ms
Request Payload.Groups Round Trip	✅	1007ms
Request Payload.Groups Default To Empty Object	✅	1007ms
Request Payload.Person Properties Distinct Id Auto Populated When Caller Omits It	✅	1007ms
Request Payload.Disable Geoip False Propagates As Geoip Disable False	✅	1007ms
Request Payload.Disable Geoip Omitted Defaults To False	✅	1007ms
Request Payload.Flag Keys To Evaluate Contains Only Requested Key	✅	1007ms
Request Lifecycle.No Flags Request On Init Alone	✅	503ms
Request Lifecycle.No Flags Request On Normal Capture	✅	1508ms
Request Lifecycle.Two Flag Calls Produce Two Remote Requests	✅	1011ms
Request Lifecycle.Mock Response Value Is Returned To Caller	✅	1003ms
Side Effect Events.Get Feature Flag Captures Feature Flag Called Event	✅	1509ms

[greptile-apps]

Prompt To Fix All With AI

Fix the following 2 code review issues. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 2
.github/scripts/check_public_api.py:253-263
The `--check` flag is defined and documented, but `args.check` is never read in the body of `main()`. The snapshot check always runs when `--write` is absent, making the flag purely cosmetic. Per the simplicity rules, superfluous parts should be removed — callers (including the Makefile) can invoke the script without `--check` and get the same behaviour.

```suggestion
    parser.add_argument(
        "--write",
        action="store_true",
        help="write the generated public API snapshot (default: check)",
    )
    args = parser.parse_args()
```

### Issue 2 of 2
.github/scripts/check_public_api.py:150
Every branch of `_record` returns a non-`None` string; the `| None` in the return type is unreachable. This misleads type checkers and readers into thinking `None` is a meaningful output, and the downstream walrus-operator filter `if (record := _record(obj))` reads as though it guards against `None` when it only ever filters empty strings (which also never occur in practice).

```suggestion
def _record(obj: object) -> str:
```

_{Reviews (1): Last reviewed commit: "ci: restore release checkout depth" | Re-trigger Greptile}

[marandaneto]

Addressed Greptile's feedback in 03bab2e: removed the unused --check CLI flag, updated the Makefile to use the implicit check mode, and simplified _record to return str with a direct sorted generator.

[greptile-apps]

_{Reviews (2): Last reviewed commit: "ci: simplify public API snapshot check C..." | Re-trigger Greptile}