Ensure openapi path params are handled properly

[jlowin]

Closes #497
Also unifies OpenAPI 3.0 and 3.1 parsing into a single generic utility

[Copilot]

Pull Request Overview

This PR adds support for properly formatting array path parameters (both simple and complex) in the OpenAPITool, and unifies parsing for OpenAPI 3.0 and 3.1.

• Implements comma-separated serialization for array path parameters, including a fallback for nested objects
• Adds unit and integration tests covering simple and complex array path parameters
• Consolidates OpenAPI version handling into a single utility

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
tests/server/test_openapi_path_parameters.py	New fixtures and tests covering array path parameters (simple and complex)
tests/server/test_openapi_array_params.py	Duplicate tests for simple array path parameter handling
src/fastmcp/server/openapi.py	Core implementation for serializing array path parameters

Comments suppressed due to low confidence (2)

src/fastmcp/server/openapi.py:189

• The isinstance check using a union type (str | int | float | bool) is not valid; use a tuple of types instead, e.g., isinstance(item, (str, int, float, bool)).

isinstance(item, str | int | float | bool)

src/fastmcp/server/openapi.py:182

• The code references param_info.schema_, but the ParameterInfo object likely defines this under schema. Please verify the correct attribute name to avoid an AttributeError at runtime.

schema = param_info.schema_

[Copilot]

Pull Request Overview

A concise utility now unifies OpenAPI 3.0 and 3.1 parsing and ensures array path and query parameters are formatted correctly.

• Handles array path parameters in “simple” style (comma-separated) when building the request path.
• Serializes array query parameters with proper explode logic or comma separation.
• Consolidates OpenAPI parsing logic into a single generic utility.

Comments suppressed due to low confidence (3)

src/fastmcp/server/openapi.py:174

• New array formatting behavior for path parameters should be covered by unit tests—add tests for simple and complex array path parameters to ensure correctness.

# Handle array path parameters with style 'simple' (comma-separated)

src/fastmcp/server/openapi.py:189

• The expression isinstance(item, str | int | float | bool) is invalid; use a tuple of types instead, e.g. isinstance(item, (str, int, float, bool)).

isinstance(item, str | int | float | bool)

src/fastmcp/server/openapi.py:259

• Same issue here: replace isinstance(item, str | int | float | bool) with isinstance(item, (str, int, float, bool)).

isinstance(item, str | int | float | bool)

[Copilot]

[nitpick] The logic for formatting complex array elements is duplicated for both path and query parameters; consider extracting it into a shared helper function to improve readability and reduce duplication.