pi-lens/rules/tree-sitter-queries/python/endpoint-204-with-body.yml

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# Invalid 204 Status Code Response Body
# Detects endpoints decorated with status_code=204 that return a non-bare value
# (204 No Content must have an empty response body)
id: endpoint-204-with-body
name: Endpoint Returning 204 with Body
severity: warning
category: reliability
defect_class: convention
inline_tier: blocking
language: python

message: "Endpoint with status_code=204 should not return a value"

description: |
  HTTP 204 No Content must have an empty response body. Returning
  a value (even None) in a 204 endpoint can confuse clients and
  proxies.

  Detection: matches a decorator that contains a call with a
  `status_code=204` keyword argument. The post_filter checks the
  decorated function body contains a `return $VALUE` statement with
  a value (not bare `return`).

  ✅ FIX: Use bare `return` or remove the status_code=204

query: |
  (decorated_definition
    (decorator
      (call
        arguments: (argument_list
          (keyword_argument
            name: (identifier) @NAME
            value: (integer) @VAL))))
    (function_definition) @FUNC) @DEC

metavars:
  - NAME
  - VAL
  - FUNC
  - DEC

post_filter: status_204_with_value_return

has_fix: false

tags:
  - reliability
  - http
  - fastapi
  - flask

examples:
  bad: |
    @app.delete("/x", status_code=204)
    def delete():
        return {"deleted": True}  # BAD - 204 must have empty body
  
  good: |
    @app.delete("/x", status_code=204)
    def delete():
        db.delete(x)
        return  # OK - bare return