Auto merge of #16209 - l1nxy:add-merge-nested-if, r=Veykril

feat: assist to merge nested if

resolve: #16095

3 files changed, 265 insertions, 0 deletions

diff --git a/crates/ide-assists/src/handlers/merge_nested_if.rs b/crates/ide-assists/src/handlers/merge_nested_if.rs
new file mode 100644
index 00000000000..2f3136f027b
--- /dev/null
+++ b/crates/ide-assists/src/handlers/merge_nested_if.rs
@@ -0,0 +1,246 @@
+use ide_db::syntax_helpers::node_ext::is_pattern_cond;
+use syntax::{
+    ast::{self, AstNode, BinaryOp},
+    T,
+};
+
+use crate::{
+    assist_context::{AssistContext, Assists},
+    AssistId, AssistKind,
+};
+// Assist: merge_nested_if
+//
+// This transforms if expressions of the form `if x { if y {A} }` into `if x && y {A}`
+// This assist can only be applied with the cursor on `if`.
+//
+// ```
+// fn main() {
+//    i$0f x == 3 { if y == 4 { 1 } }
+// }
+// ```
+// ->
+// ```
+// fn main() {
+//    if x == 3 && y == 4 { 1 }
+// }
+// ```
+pub(crate) fn merge_nested_if(acc: &mut Assists, ctx: &AssistContext<'_>) -> Option<()> {
+    let if_keyword = ctx.find_token_syntax_at_offset(T![if])?;
+    let expr = ast::IfExpr::cast(if_keyword.parent()?)?;
+    let if_range = if_keyword.text_range();
+    let cursor_in_range = if_range.contains_range(ctx.selection_trimmed());
+    if !cursor_in_range {
+        return None;
+    }
+
+    //should not apply to if with else branch.
+    if expr.else_branch().is_some() {
+        return None;
+    }
+
+    let cond = expr.condition()?;
+    //should not apply for if-let
+    if is_pattern_cond(cond.clone()) {
+        return None;
+    }
+
+    let cond_range = cond.syntax().text_range();
+
+    //check if the then branch is a nested if
+    let then_branch = expr.then_branch()?;
+    let stmt = then_branch.stmt_list()?;
+    if stmt.statements().count() != 0 {
+        return None;
+    }
+
+    let nested_if_to_merge = then_branch.tail_expr().and_then(|e| match e {
+        ast::Expr::IfExpr(e) => Some(e),
+        _ => None,
+    })?;
+    // should not apply to nested if with else branch.
+    if nested_if_to_merge.else_branch().is_some() {
+        return None;
+    }
+    let nested_if_cond = nested_if_to_merge.condition()?;
+    if is_pattern_cond(nested_if_cond.clone()) {
+        return None;
+    }
+
+    let nested_if_then_branch = nested_if_to_merge.then_branch()?;
+    let then_branch_range = then_branch.syntax().text_range();
+
+    acc.add(
+        AssistId("merge_nested_if", AssistKind::RefactorRewrite),
+        "Merge nested if",
+        if_range,
+        |edit| {
+            let cond_text = if has_logic_op_or(&cond) {
+                format!("({})", cond.syntax().text())
+            } else {
+                cond.syntax().text().to_string()
+            };
+
+            let nested_if_cond_text = if has_logic_op_or(&nested_if_cond) {
+                format!("({})", nested_if_cond.syntax().text())
+            } else {
+                nested_if_cond.syntax().text().to_string()
+            };
+
+            let replace_cond = format!("{} && {}", cond_text, nested_if_cond_text);
+
+            edit.replace(cond_range, replace_cond);
+            edit.replace(then_branch_range, nested_if_then_branch.syntax().text());
+        },
+    )
+}
+
+/// Returns whether the given if condition has logical operators.
+fn has_logic_op_or(expr: &ast::Expr) -> bool {
+    match expr {
+        ast::Expr::BinExpr(bin_expr) => {
+            if let Some(kind) = bin_expr.op_kind() {
+                matches!(kind, BinaryOp::LogicOp(ast::LogicOp::Or))
+            } else {
+                false
+            }
+        }
+        _ => false,
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::tests::{check_assist, check_assist_not_applicable};
+
+    #[test]
+    fn merge_nested_if_test1() {
+        check_assist(
+            merge_nested_if,
+            "fn f() { i$0f x == 3 { if y == 4 { 1 } } }",
+            "fn f() { if x == 3 && y == 4 { 1 } }",
+        )
+    }
+
+    #[test]
+    fn merge_nested_if_test2() {
+        check_assist(
+            merge_nested_if,
+            "fn f() { i$0f x == 3 || y == 1 { if z == 4 { 1 } } }",
+            "fn f() { if (x == 3 || y == 1) && z == 4 { 1 } }",
+        )
+    }
+
+    #[test]
+    fn merge_nested_if_test3() {
+        check_assist(
+            merge_nested_if,
+            "fn f() { i$0f x == 3 && y == 1 { if z == 4 { 1 } } }",
+            "fn f() { if x == 3 && y == 1 && z == 4 { 1 } }",
+        )
+    }
+
+    #[test]
+    fn merge_nested_if_test4() {
+        check_assist(
+            merge_nested_if,
+            "fn f() { i$0f x == 3 && y == 1 { if z == 4 && q == 3 { 1 } } }",
+            "fn f() { if x == 3 && y == 1 && z == 4 && q == 3 { 1 } }",
+        )
+    }
+
+    #[test]
+    fn merge_nested_if_test5() {
+        check_assist(
+            merge_nested_if,
+            "fn f() { i$0f x == 3 && y == 1 { if z == 4 || q == 3 { 1 } } }",
+            "fn f() { if x == 3 && y == 1 && (z == 4 || q == 3) { 1 } }",
+        )
+    }
+
+    #[test]
+    fn merge_nested_if_test6() {
+        check_assist(
+            merge_nested_if,
+            "fn f() { i$0f x == 3 || y == 1 { if z == 4 || q == 3 { 1 } } }",
+            "fn f() { if (x == 3 || y == 1) && (z == 4 || q == 3) { 1 } }",
+        )
+    }
+
+    #[test]
+    fn merge_nested_if_test7() {
+        check_assist(
+            merge_nested_if,
+            "fn f() { i$0f x == 3 || y == 1 { if z == 4 && q == 3 { 1 } } }",
+            "fn f() { if (x == 3 || y == 1) && z == 4 && q == 3 { 1 } }",
+        )
+    }
+
+    #[test]
+    fn merge_nested_if_do_not_apply_to_if_with_else_branch() {
+        check_assist_not_applicable(
+            merge_nested_if,
+            "fn f() { i$0f x == 3 { if y == 4 { 1 } } else { 2 } }",
+        )
+    }
+
+    #[test]
+    fn merge_nested_if_do_not_apply_to_nested_if_with_else_branch() {
+        check_assist_not_applicable(
+            merge_nested_if,
+            "fn f() { i$0f x == 3 { if y == 4 { 1 } else { 2 } } }",
+        )
+    }
+
+    #[test]
+    fn merge_nested_if_do_not_apply_to_if_let() {
+        check_assist_not_applicable(
+            merge_nested_if,
+            "fn f() { i$0f let Some(x) = y { if x == 4 { 1 } } }",
+        )
+    }
+
+    #[test]
+    fn merge_nested_if_do_not_apply_to_nested_if_let() {
+        check_assist_not_applicable(
+            merge_nested_if,
+            "fn f() { i$0f y == 0 { if let Some(x) = y { 1 } } }",
+        )
+    }
+
+    #[test]
+    fn merge_nested_if_do_not_apply_to_if_with_else_branch_and_nested_if() {
+        check_assist_not_applicable(
+            merge_nested_if,
+            "fn f() { i$0f x == 3 { if y == 4 { 1 } } else { if z == 5 { 2 } } }",
+        )
+    }
+
+    #[test]
+    fn merge_nested_if_do_not_apply_with_cursor_not_on_if() {
+        check_assist_not_applicable(merge_nested_if, "fn f() { if $0x==0 { if y == 3 { 1 } } }")
+    }
+
+    #[test]
+    fn merge_nested_if_do_not_apply_with_mulpiple_if() {
+        check_assist_not_applicable(
+            merge_nested_if,
+            "fn f() { i$0f x == 0 { if y == 3 { 1 } else if y == 4 { 2 } } }",
+        )
+    }
+    #[test]
+    fn merge_nested_if_do_not_apply_with_not_only_has_nested_if() {
+        check_assist_not_applicable(
+            merge_nested_if,
+            "fn f() { i$0f x == 0 { if y == 3 { foo(); } foo(); } }",
+        )
+    }
+
+    #[test]
+    fn merge_nested_if_do_not_apply_with_multiply_nested_if() {
+        check_assist_not_applicable(
+            merge_nested_if,
+            "fn f() { i$0f x == 0 { if y == 3 { foo(); } if z == 3 { 2 } } }",
+        )
+    }
+}
diff --git a/crates/ide-assists/src/lib.rs b/crates/ide-assists/src/lib.rs
index 1e4d1c94f5b..1eb4903ab20 100644
--- a/crates/ide-assists/src/lib.rs
+++ b/crates/ide-assists/src/lib.rs
@@ -217,6 +217,7 @@ mod handlers {
     mod unqualify_method_call;
     mod wrap_return_type_in_result;
     mod into_to_qualified_from;
+    mod merge_nested_if;
 
     pub(crate) fn all() -> &'static [Handler] {
         &[
@@ -291,6 +292,7 @@ mod handlers {
             invert_if::invert_if,
             merge_imports::merge_imports,
             merge_match_arms::merge_match_arms,
+            merge_nested_if::merge_nested_if,
             move_bounds::move_bounds_to_where_clause,
             move_const_to_impl::move_const_to_impl,
             move_guard::move_arm_cond_to_match_guard,
diff --git a/crates/ide-assists/src/tests/generated.rs b/crates/ide-assists/src/tests/generated.rs
index 0c2331796f9..0ce89ae0a9a 100644
--- a/crates/ide-assists/src/tests/generated.rs
+++ b/crates/ide-assists/src/tests/generated.rs
@@ -2052,6 +2052,23 @@ fn handle(action: Action) {
 }
 
 #[test]
+fn doctest_merge_nested_if() {
+    check_doc_test(
+        "merge_nested_if",
+        r#####"
+fn main() {
+   i$0f x == 3 { if y == 4 { 1 } }
+}
+"#####,
+        r#####"
+fn main() {
+   if x == 3 && y == 4 { 1 }
+}
+"#####,
+    )
+}
+
+#[test]
 fn doctest_move_arm_cond_to_match_guard() {
     check_doc_test(
         "move_arm_cond_to_match_guard",