Handle UP032 autofix with adjacent keywords (#3636)

crates/ruff/resources/test/fixtures/pyupgrade/UP032.py

@@ -86,3 +86,14 @@ async def c():
 
 async def c():
     return "{}".format(1 + await 3)
+
+
+def d(osname, version, release):
+    return"{}-{}.{}".format(osname, version, release)
+
+
+def e():
+    yield"{}".format(1)
+
+
+assert"{}".format(1)

crates/ruff/src/rules/pyupgrade/rules/f_strings.rs

@@ -2,7 +2,7 @@ use rustc_hash::FxHashMap;
 use rustpython_common::format::{
     FieldName, FieldNamePart, FieldType, FormatPart, FormatString, FromTemplate,
 };
-use rustpython_parser::ast::{Constant, Expr, ExprKind, KeywordData};
+use rustpython_parser::ast::{Constant, Expr, ExprKind, KeywordData, Location};
 
 use ruff_diagnostics::{AlwaysAutofixableViolation, Diagnostic, Fix};
 use ruff_macros::{derive_message_formats, violation};
@@ -247,7 +247,7 @@ pub(crate) fn f_strings(checker: &mut Checker, summary: &FormatSummary, expr: &E
 
     // Currently, the only issue we know of is in LibCST:
     // https://github.com/Instagram/LibCST/issues/846
-    let Some(contents) = try_convert_to_f_string(checker, expr) else {
+    let Some(mut contents) = try_convert_to_f_string(checker, expr) else {
         return;
     };
 
@@ -257,6 +257,18 @@ pub(crate) fn f_strings(checker: &mut Checker, summary: &FormatSummary, expr: &E
         return;
     }
 
+    // If necessary, add a space between any leading keyword (`return`, `yield`, `assert`, etc.)
+    // and the string. For example, `return"foo"` is valid, but `returnf"foo"` is not.
+    if expr.location.column() > 0 {
+        let existing = checker.locator.slice(Range::new(
+            Location::new(expr.location.row(), expr.location.column() - 1),
+            expr.end_location.unwrap(),
+        ));
+        if existing.chars().next().unwrap().is_ascii_alphabetic() {
+            contents.insert(0, ' ');
+        }
+    }
+
     let mut diagnostic = Diagnostic::new(FString, Range::from(expr));
     if checker.patch(diagnostic.kind.rule()) {
         diagnostic.amend(Fix::replacement(

crates/ruff/src/rules/pyupgrade/snapshots/ruff__rules__pyupgrade__tests__UP032.py.snap

@@ -442,4 +442,64 @@ expression: diagnostics
       row: 47
       column: 24
   parent: ~
+- kind:
+    name: FString
+    body: "Use f-string instead of `format` call"
+    suggestion: Convert to f-string
+    fixable: true
+  location:
+    row: 92
+    column: 10
+  end_location:
+    row: 92
+    column: 53
+  fix:
+    content: " f\"{osname}-{version}.{release}\""
+    location:
+      row: 92
+      column: 10
+    end_location:
+      row: 92
+      column: 53
+  parent: ~
+- kind:
+    name: FString
+    body: "Use f-string instead of `format` call"
+    suggestion: Convert to f-string
+    fixable: true
+  location:
+    row: 96
+    column: 9
+  end_location:
+    row: 96
+    column: 23
+  fix:
+    content: " f\"{1}\""
+    location:
+      row: 96
+      column: 9
+    end_location:
+      row: 96
+      column: 23
+  parent: ~
+- kind:
+    name: FString
+    body: "Use f-string instead of `format` call"
+    suggestion: Convert to f-string
+    fixable: true
+  location:
+    row: 99
+    column: 6
+  end_location:
+    row: 99
+    column: 20
+  fix:
+    content: " f\"{1}\""
+    location:
+      row: 99
+      column: 6
+    end_location:
+      row: 99
+      column: 20
+  parent: ~