[BUG] [RUST] Missing lifetime when using mockall feature and optional query parameter

[ThaddeusTreloar]

Bug Report Checklist

• [*] Have you provided a full/minimal spec to reproduce the issue?
• [*] Have you validated the input using an OpenAPI validator?
• [*] Have you tested with the latest master to confirm the issue still exists?
• [*] Have you searched for related issues/PRs?
• [*] What's the actual output vs expected output?
• [Optional] Sponsorship to speed up the bug fix or feature request (example)

Description

When generating using the reqwest-trait library and mockall feature (uses the mockall::automock procedural macro), the lifetime annotations in the function signature causing compilation to fail.

openapi-generator version

docker: openapitools/openapi-generator-cli:latest

OpenAPI declaration file content or url

openapi: 3.0.3
info:
  title: Mockall lifetime bu
  description: >-
    An optional string query parameter causes the generator to declare a named
    lifetime (e.g. 'run_id) in the async fn generics but emit Option<&str>
    (anonymous lifetime) instead of Option<&'run_id str>. The #[automock]
    macro cannot elide the lifetime.
  version: 1.0.0
servers:
  - url: /api/v1
paths:
  /widgets/{id}/items:
    parameters:
      - name: id
        in: path
        required: true
        schema:
          type: string
          format: uuid
    get:
      operationId: listWidgetItems
      summary: List items for a widget, optionally filtered by run_id
      tags:
        - widget
      parameters:
        - name: run_id
          in: query
          required: false
          description: Optional string query param — triggers the lifetime bug when mockall=true
          schema:
            type: string
            format: uuid
      responses:
        "200":
          description: Item list
          content:
            application/json:
              schema:
                type: object
                required:
                  - items
                properties:
                  items:
                    type: array
                    items:
                      $ref: "#/components/schemas/Item"
components:
  schemas:
    Item:
      type: object
      required:
        - id
      properties:
        id:
          type: string
          format: uuid

Generation Details

podman run --rm -v "$PWD":/local openapitools/openapi-generator-cli:latest generate \
	    -i /local/bug/v1/spec.yaml \
	    -g rust \
	    -o /local/target/spec-lib-rs-client-bug \
	    --additional-properties packageName=spec-lib-rs-client-bug,packageVersion=1.0.0,supportMiddleware=true,reqwestDefaultFeatures=rustls,library=reqwest-trait,mockall=true

Steps to reproduce

Run the provided command with the provided spec as the target. Then attempt to build the library using:

cargo build --features mockall

The output should be:

error[E0106]: missing lifetime specifier
  --> src/apis/widget_api.rs:29:78
   |
29 |     async fn list_widget_items<'id, 'run_id>(&self, id: &str, run_id: Option<&str>) -> Result<models::ListWidgetItems200Resp...
   |                                                                              ^ expected named lifetime parameter
   |
   = note: for more information on higher-ranked polymorphism, visit https://doc.rust-lang.org/nomicon/hrtb.html
help: consider making the bound lifetime-generic with a new `'a` lifetime
   |
22 ~ #[cfg_attr(feature = "mockall", for<'a> automock)]
23 | #[async_trait]
...
28 |     ///
29 ~     async fn list_widget_items<'id, 'run_id>(&self, id: &str, run_id: Option<&'a str>) -> Result<models::ListWidgetItems200Response, Error<ListWidgetItemsError>>;
   |
help: consider introducing a named lifetime parameter
   |
22 ~ #[cfg_attr(feature = "mockall", automock<'a>)]
23 | #[async_trait]
...
28 |     ///
29 ~     async fn list_widget_items<'id, 'run_id>(&self, id: &str, run_id: Option<&'a str>) -> Result<models::ListWidgetItems200Response, Error<ListWidgetItemsError>>;
   |

error[E0637]: `&` without an explicit lifetime name cannot be used here
  --> src/apis/widget_api.rs:29:78
   |
29 |     async fn list_widget_items<'id, 'run_id>(&self, id: &str, run_id: Option<&str>) -> Result<models::ListWidgetItems200Resp...
   |                                                                              ^ explicit lifetime name needed here
   |
help: consider introducing a higher-ranked lifetime here
   |
22 ~ #[cfg_attr(feature = "mockall", for<'a> automock)]
23 | #[async_trait]
...
28 |     ///
29 ~     async fn list_widget_items<'id, 'run_id>(&self, id: &str, run_id: Option<&'a str>) -> Result<models::ListWidgetItems200Response, Error<ListWidgetItemsError>>;
   |

Some errors have detailed explanations: E0106, E0637.
For more information about an error, try `rustc --explain E0106`.
error: could not compile `spec-lib-rs-client-bug` (lib) due to 2 previous errors