feat: Added an extensible API for stream schema sources

[edgarrmondragon]

Summary by Sourcery

Introduce an extensible API for stream schema sources.

New Features:

• Add LocalSchemaSource to load schemas from local files.
• Add OpenAPISchemaSource to load schemas from OpenAPI specs.

Tests:

• Add tests for LocalSchemaSource and OpenAPISchemaSource.

---

📚 Documentation preview 📚: https://meltano-sdk--2876.org.readthedocs.build/en/2876/

[sourcery-ai[bot]]

Reviewer's Guide

This PR adds a pluggable schema source API by defining a BaseSchemaSource with Local and OpenAPI implementations, updates existing taps and tests to consume the new API, and includes necessary test fixtures.

Class diagram for the new extensible schema source API

classDiagram
    class BaseSchemaSource {
        - _registry: dict[str, dict]
        + __init__()
        + get_schema(*args, **kwargs) dict
        + __call__(*args, **kwargs) dict
    }
    class LocalSchemaSource {
        - path: Path | Traversable
        + __init__(path)
        + get_schema(name: str) dict
    }
    class OpenAPISchemaSource {
        - path: str | Path | Traversable
        + __init__(path)
        + spec_dict: dict (cached_property)
        + get_schema(ref: str) dict
    }
    BaseSchemaSource <|-- LocalSchemaSource
    BaseSchemaSource <|-- OpenAPISchemaSource

Class diagram for updated stream schema usage in sample_tap_gitlab

classDiagram
    class ProjectsStream {
        + schema: dict
    }
    class ReleasesStream {
        + schema: dict
    }
    class IssuesStream {
        + schema: dict
    }
    class CommitsStream {
        + schema: dict
    }
    class EpicsStream {
        + schema: dict
    }
    class EpicIssuesStream {
        + schema: dict
    }
    note for ProjectsStream "schema now set via LocalSchemaSource('projects')"
    note for ReleasesStream "schema now set via LocalSchemaSource('releases')"
    note for IssuesStream "schema now set via LocalSchemaSource('issues')"
    note for CommitsStream "schema now set via LocalSchemaSource('commits')"
    note for EpicsStream "schema now set via LocalSchemaSource('epics')"
    note for EpicIssuesStream "schema now set via LocalSchemaSource('epic_issues')"

File-Level Changes

Change	Details	Files
Introduce extensible schema source API	Add BaseSchemaSource abstraction with registry and call hook Implement LocalSchemaSource loading JSON files lazily Implement OpenAPISchemaSource fetching spec and resolving references	singer_sdk/schema.py
Update sample GitLab tap to use LocalSchemaSource	Import and instantiate LocalSchemaSource as LOCAL_SCHEMAS Replace schema_filepath assignments with schema = LOCAL_SCHEMAS(...) calls	samples/sample_tap_gitlab/gitlab_rest_streams.py
Refactor tests to cover new schema sources	Remove legacy Schema.from_dict tests from core tests and add Local/OpenAPI source tests Relocate simple_schema and schema_with_items tests to singerlib tests and update imports	tests/core/test_schema.py tests/singerlib/test_schema.py
Add test fixtures for schemas	Provide an OpenAPI spec fixture (openapi.json) Provide a local JSON schema fixture (user.json)	tests/fixtures/openapi.json tests/fixtures/schemas/user.json

Possibly linked issues

• #0: PR adds API and local/OpenAPI sources for issue's schema source feature request.

---

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[codecov[bot]]

Codecov Report

:white_check_mark: All modified and coverable lines are covered by tests. :white_check_mark: Project coverage is 92.30%. Comparing base (bb957f0) to head (4692d5a). :warning: Report is 43 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2876   +/-   ##
=======================================
  Coverage   92.30%   92.30%           
=======================================
  Files          63       63           
  Lines        5343     5343           
  Branches      677      677           
=======================================
  Hits         4932     4932           
  Misses        290      290           
  Partials      121      121           

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[codspeed-hq[bot]]

CodSpeed Performance Report

Merging #2876 will not alter performance

_{Comparing 2746-feat-add-an-extensible-api-for-stream-schema-sources (4692d5a) with main (1495d93)}

Summary

✅ 8 untouched benchmarks

[peterclemenko]

I agree with this, especially if it opens the door to graphql subscriptions

[edgarrmondragon]

I agree with this, especially if it opens the door to graphql subscriptions

Can you say more about that? How do you think this could make it easier to subscribe to live updates?

[peterclemenko]

I agree with this, especially if it opens the door to graphql subscriptions

Can you say more about that? How do you think this could make it easier to subscribe to live updates?

I might be misinterpreting the intention of this pull, nevermind.

[edgarrmondragon]

@sourcery-ai review