Fix SIM102 to handle indented elif (#6072)

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## Summary

<!-- What's the purpose of the change? What does it do, and why? -->

The `SIM102` auto-fix fails if `elif` is indented like this:

## Example

```python
def f():
    # SIM102
    if a:
        pass
    elif b:
        if c:
            d
```

```
> cargo run -p ruff_cli -- check --select SIM102 --fix a.py
...
error: Failed to fix nested if: Failed to extract statement from source
a.py:5:5: SIM102 Use a single `if` statement instead of nested `if` statements
Found 1 error.
```

## Test Plan

<!-- How was it tested? -->

New test

crates/ruff/resources/test/fixtures/flake8_simplify/SIM102.py

@@ -156,3 +156,12 @@
 if True:
     if a:
         pass
+
+
+# SIM102
+def f():
+    if a:
+        pass
+    elif b:
+        if c:
+            d

crates/ruff/src/rules/flake8_simplify/rules/ast_if.rs

@@ -312,7 +312,8 @@ fn find_last_nested_if(body: &[Stmt]) -> Option<(&Expr, &Stmt)> {
     })
 }
 
-fn nested_if_body(stmt_if: &StmtIf) -> Option<(&[Stmt], TextRange)> {
+/// Returns the body, the range of the `if` or `elif` and whether the range is for an `if` or `elif`
+fn nested_if_body(stmt_if: &StmtIf) -> Option<(&[Stmt], TextRange, bool)> {
     let StmtIf {
         test,
         body,
@@ -322,15 +323,15 @@ fn nested_if_body(stmt_if: &StmtIf) -> Option<(&[Stmt], TextRange)> {
 
     // It must be the last condition, otherwise there could be another `elif` or `else` that only
     // depends on the outer of the two conditions
-    let (test, body, range) = if let Some(clause) = elif_else_clauses.last() {
+    let (test, body, range, is_elif) = if let Some(clause) = elif_else_clauses.last() {
         if let Some(test) = &clause.test {
-            (test, &clause.body, clause.range())
+            (test, &clause.body, clause.range(), true)
         } else {
             // The last condition is an `else` (different rule)
             return None;
         }
     } else {
-        (test.as_ref(), body, stmt_if.range())
+        (test.as_ref(), body, stmt_if.range(), false)
     };
 
     // The nested if must be the only child, otherwise there is at least one more statement that
@@ -355,12 +356,12 @@ fn nested_if_body(stmt_if: &StmtIf) -> Option<(&[Stmt], TextRange)> {
         return None;
     }
 
-    Some((body, range))
+    Some((body, range, is_elif))
 }
 
 /// SIM102
 pub(crate) fn nested_if_statements(checker: &mut Checker, stmt_if: &StmtIf, parent: Option<&Stmt>) {
-    let Some((body, range)) = nested_if_body(stmt_if) else {
+    let Some((body, range, is_elif)) = nested_if_body(stmt_if) else {
         return;
     };
 
@@ -376,7 +377,7 @@ pub(crate) fn nested_if_statements(checker: &mut Checker, stmt_if: &StmtIf, pare
 
     // Check if the parent is already emitting a larger diagnostic including this if statement
     if let Some(Stmt::If(stmt_if)) = parent {
-        if let Some((body, _range)) = nested_if_body(stmt_if) {
+        if let Some((body, _range, _is_elif)) = nested_if_body(stmt_if) {
             // In addition to repeating the `nested_if_body` and `find_last_nested_if` check, we
             // also need to be the first child in the parent
             if matches!(&body[0], Stmt::If(inner) if inner == stmt_if)
@@ -400,7 +401,12 @@ pub(crate) fn nested_if_statements(checker: &mut Checker, stmt_if: &StmtIf, pare
             .comment_ranges()
             .intersects(TextRange::new(range.start(), nested_if.start()))
         {
-            match fix_if::fix_nested_if_statements(checker.locator(), checker.stylist(), range) {
+            match fix_if::fix_nested_if_statements(
+                checker.locator(),
+                checker.stylist(),
+                range,
+                is_elif,
+            ) {
                 Ok(edit) => {
                     if edit
                         .content()

crates/ruff/src/rules/flake8_simplify/rules/fix_if.rs

@@ -34,6 +34,7 @@ pub(crate) fn fix_nested_if_statements(
     locator: &Locator,
     stylist: &Stylist,
     range: TextRange,
+    is_elif: bool,
 ) -> Result<Edit> {
     // Infer the indentation of the outer block.
     let Some(outer_indent) = whitespace::indentation(locator, &range) else {
@@ -45,7 +46,6 @@ pub(crate) fn fix_nested_if_statements(
 
     // If this is an `elif`, we have to remove the `elif` keyword for now. (We'll
     // restore the `el` later on.)
-    let is_elif = contents.starts_with("elif");
     let module_text = if is_elif {
         Cow::Owned(contents.replacen("elif", "if", 1))
     } else {

crates/ruff/src/rules/flake8_simplify/snapshots/ruff__rules__flake8_simplify__tests__SIM102_SIM102.py.snap

@@ -332,4 +332,26 @@ SIM102.py:132:5: SIM102 [*] Use a single `if` statement instead of nested `if` s
 136 135 |     print("bar")
 137 136 | 
 
+SIM102.py:165:5: SIM102 [*] Use a single `if` statement instead of nested `if` statements
+    |
+163 |       if a:
+164 |           pass
+165 |       elif b:
+    |  _____^
+166 | |         if c:
+    | |_____________^ SIM102
+167 |               d
+    |
+    = help: Combine `if` statements using `and`
+
+ℹ Suggested fix
+162 162 | def f():
+163 163 |     if a:
+164 164 |         pass
+165     |-    elif b:
+166     |-        if c:
+167     |-            d
+    165 |+    elif b and c:
+    166 |+        d
+