Summary

Fixes #760 - The oasdiff breaking command was not detecting when maxItems is decreased on array query parameters because the checker was looking in the wrong location in the schema structure.

Problem

When maxItems is set directly on an array parameter schema (the correct location per OpenAPI spec), the checker failed to detect changes. For example:

parameters:
  - name: ids
    in: query
    schema:
      type: array
      maxItems: 50  # <-- maxItems here (on the array schema)
      items:
        type: string

When maxItems changed from 50 to 10, oasdiff diff would report it, but oasdiff breaking would not flag it as a breaking change.

Root Cause

The checker was only looking for maxItems in paramDiff.SchemaDiff.ItemsDiff.MaxItemsDiff (on the items schema) but not in paramDiff.SchemaDiff.MaxItemsDiff (on the parameter schema itself).

This worked for a legacy pattern where maxItems was incorrectly placed on the items schema, but failed for the correct OpenAPI specification pattern.

Solution

Updated RequestParameterMaxItemsUpdatedCheck to check both locations:

1. First: Check maxItems on the parameter schema itself (correct per spec)
2. Fallback: Check maxItems on the items schema (for backward compatibility)

Changes

• checker/check_request_parameters_max_items_updated.go: Updated logic to check both locations
• checker/check_request_parameters_max_items_updated_test.go: Added TestRequestParameterArrayMaxItemsDecreased
• data/checker/request_parameter_array_max_items_*.yaml: Added test fixtures

Testing

• ✅ New test TestRequestParameterArrayMaxItemsDecreased passes
• ✅ All existing maxItems tests pass
• ✅ Full checker test suite passes

Test plan

• Run maxItems tests: go test github.com/oasdiff/oasdiff/checker -run ".*MaxItems" -v
• Run full checker suite: go test github.com/oasdiff/oasdiff/checker
• Verify the fix resolves issue Decreasing maxItems not a breaking change? #760 scenario

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