[FastAPI] Add sub-diagnostic explaining why a fix was unavailable (FAST002) (#22565)

11happy · web-flow · commit a39a1df2bd9f · 2026-01-27T12:55:50.000-05:00
## Summary This PR fixes #22188 by adding autofix skipped reason as diagnostic info. ## Test Plan snapshots are updated accordingly. --------- Signed-off-by: Bhuminjay <bhuminjaysoni@gmail.com>
diff --git a/crates/ruff_linter/src/rules/fastapi/rules/fastapi_non_annotated_dependency.rs b/crates/ruff_linter/src/rules/fastapi/rules/fastapi_non_annotated_dependency.rs
@@ -284,6 +284,7 @@ fn create_diagnostic(
 
                 if is_default_argument_ellipsis && seen_default {
                     // For ellipsis after a parameter with default, can't remove the default
+                    diagnostic.info("Automatic fix is unavailable because a required parameter would follow an optional parameter. Consider reordering arguments to enable the fix.");
                     return Ok(None);
                 }
 
@@ -315,6 +316,7 @@ fn create_diagnostic(
             }
             _ => {
                 if seen_default {
+                    diagnostic.info("Automatic fix is unavailable because a required parameter would follow an optional parameter. Consider reordering arguments to enable the fix.");
                     return Ok(None);
                 }
                 format!(
diff --git a/crates/ruff_linter/src/rules/fastapi/snapshots/ruff_linter__rules__fastapi__tests__fast-api-non-annotated-dependency_FAST002_0.py.snap b/crates/ruff_linter/src/rules/fastapi/snapshots/ruff_linter__rules__fastapi__tests__fast-api-non-annotated-dependency_FAST002_0.py.snap
@@ -358,3 +358,4 @@ FAST002 FastAPI dependency without `Annotated`
 72 |     pass
    |
 help: Replace with `typing.Annotated`
+info: Automatic fix is unavailable because a required parameter would follow an optional parameter. Consider reordering arguments to enable the fix.
diff --git a/crates/ruff_linter/src/rules/fastapi/snapshots/ruff_linter__rules__fastapi__tests__fast-api-non-annotated-dependency_FAST002_0.py_py38.snap b/crates/ruff_linter/src/rules/fastapi/snapshots/ruff_linter__rules__fastapi__tests__fast-api-non-annotated-dependency_FAST002_0.py_py38.snap
@@ -358,3 +358,4 @@ FAST002 FastAPI dependency without `Annotated`
 72 |     pass
    |
 help: Replace with `typing_extensions.Annotated`
+info: Automatic fix is unavailable because a required parameter would follow an optional parameter. Consider reordering arguments to enable the fix.
diff --git a/crates/ruff_linter/src/rules/fastapi/snapshots/ruff_linter__rules__fastapi__tests__fast-api-non-annotated-dependency_FAST002_2.py.snap b/crates/ruff_linter/src/rules/fastapi/snapshots/ruff_linter__rules__fastapi__tests__fast-api-non-annotated-dependency_FAST002_2.py.snap
@@ -273,6 +273,7 @@ FAST002 FastAPI dependency without `Annotated`
 85 |     another_optional_param: int = Query(42, description="Another optional"),
    |
 help: Replace with `typing.Annotated`
+info: Automatic fix is unavailable because a required parameter would follow an optional parameter. Consider reordering arguments to enable the fix.
 
 FAST002 [*] FastAPI dependency without `Annotated`
   --> FAST002_2.py:85:5
diff --git a/crates/ruff_linter/src/rules/fastapi/snapshots/ruff_linter__rules__fastapi__tests__fast-api-non-annotated-dependency_FAST002_2.py_py38.snap b/crates/ruff_linter/src/rules/fastapi/snapshots/ruff_linter__rules__fastapi__tests__fast-api-non-annotated-dependency_FAST002_2.py_py38.snap
@@ -273,6 +273,7 @@ FAST002 FastAPI dependency without `Annotated`
 85 |     another_optional_param: int = Query(42, description="Another optional"),
    |
 help: Replace with `typing_extensions.Annotated`
+info: Automatic fix is unavailable because a required parameter would follow an optional parameter. Consider reordering arguments to enable the fix.
 
 FAST002 [*] FastAPI dependency without `Annotated`
   --> FAST002_2.py:85:5

Original file line number	Diff line number	Diff line change
`@@ -284,6 +284,7 @@ fn create_diagnostic(`
`284`	`284`
`285`	`285`	`if is_default_argument_ellipsis && seen_default {`
`286`	`286`	`// For ellipsis after a parameter with default, can't remove the default`
	`287`	`+ diagnostic.info("Automatic fix is unavailable because a required parameter would follow an optional parameter. Consider reordering arguments to enable the fix.");`
`287`	`288`	`return Ok(None);`
`288`	`289`	`}`
`289`	`290`
`@@ -315,6 +316,7 @@ fn create_diagnostic(`
`315`	`316`	`}`
`316`	`317`	`_ => {`
`317`	`318`	`if seen_default {`
	`319`	`+ diagnostic.info("Automatic fix is unavailable because a required parameter would follow an optional parameter. Consider reordering arguments to enable the fix.");`
`318`	`320`	`return Ok(None);`
`319`	`321`	`}`
`320`	`322`	`format!(`
Original file line number	Diff line number	Diff line change
@@ -358,3 +358,4 @@ FAST002 FastAPI dependency without `Annotated`
`358`	`358`	`72 \| pass`
`359`	`359`	`\|`
`360`	`360`	help: Replace with `typing.Annotated`
	`361`	`+info: Automatic fix is unavailable because a required parameter would follow an optional parameter. Consider reordering arguments to enable the fix.`
Original file line number	Diff line number	Diff line change
@@ -273,6 +273,7 @@ FAST002 FastAPI dependency without `Annotated`
`273`	`273`	`85 \| another_optional_param: int = Query(42, description="Another optional"),`
`274`	`274`	`\|`
`275`	`275`	help: Replace with `typing.Annotated`
	`276`	`+info: Automatic fix is unavailable because a required parameter would follow an optional parameter. Consider reordering arguments to enable the fix.`
`276`	`277`
`277`	`278`	FAST002 [*] FastAPI dependency without `Annotated`
`278`	`279`	`--> FAST002_2.py:85:5`