feat: add assist to convert char literal

crates/ide-assists/src/handlers/convert_char_literal.rs

@@ -0,0 +1,97 @@
+use syntax::{AstToken, ast};
+
+use crate::{AssistContext, AssistId, Assists, GroupLabel};
+
+// Assist: convert_char_literal
+//
+// Converts character literals between different representations. Currently supports normal character -> ASCII / Unicode escape.
+// ```
+// const _: char = 'a'$0;
+// ```
+// ->
+// ```
+// const _: char = '\x61';
+// ```
+pub(crate) fn convert_char_literal(acc: &mut Assists, ctx: &AssistContext<'_>) -> Option<()> {
+    if !ctx.has_empty_selection() {
+        return None;
+    }
+
+    let literal = ctx.find_node_at_offset::<ast::Literal>()?;
+    let literal = match literal.kind() {
+        ast::LiteralKind::Char(it) => it,
+        _ => return None,
+    };
+
+    let value = literal.value().ok()?;
+    let text = literal.syntax().text().to_owned();
+    let range = literal.syntax().text_range();
+    let group_id = GroupLabel("Convert char representation".into());
+
+    let mut add_assist = |converted: String| {
+        // Skip no-op assists (e.g. `'const C: char = '\\x61';'` already matches the ASCII form).
+        if converted == text {
+            return;
+        }
+        let label = format!("Convert {text} to {converted}");
+        acc.add_group(
+            &group_id,
+            AssistId::refactor_rewrite("convert_char_literal"),
+            label,
+            range,
+            |builder| builder.replace(range, converted),
+        );
+    };
+
+    if value.is_ascii() {
+        add_assist(format!("'\\x{:02x}'", value as u32));
+    }
+
+    add_assist(format!("'\\u{{{:x}}}'", value as u32));
+
+    Some(())
+}
+
+#[cfg(test)]
+mod tests {
+    use crate::tests::check_assist_by_label;
+
+    use super::convert_char_literal;
+
+    #[test]
+    fn ascii_char_to_ascii_and_unicode() {
+        let before = "const _: char = 'a'$0;";
+        check_assist_by_label(
+            convert_char_literal,
+            before,
+            "const _: char = '\\x61';",
+            "Convert 'a' to '\\x61'",
+        );
+        check_assist_by_label(
+            convert_char_literal,
+            before,
+            "const _: char = '\\u{61}';",
+            "Convert 'a' to '\\u{61}'",
+        );
+    }
+
+    #[test]
+    fn non_ascii_char_only_unicode() {
+        check_assist_by_label(
+            convert_char_literal,
+            "const _: char = '😀'$0;",
+            "const _: char = '\\u{1f600}';",
+            "Convert '😀' to '\\u{1f600}'",
+        );
+    }
+
+    #[test]
+    fn ascii_escape_can_convert_to_unicode() {
+        check_assist_by_label(
+            convert_char_literal,
+            "const _: char = '\\x61'$0;",
+            "const _: char = '\\u{61}';",
+            "Convert '\\x61' to '\\u{61}'",
+        );
+    }
+}

crates/ide-assists/src/lib.rs

@@ -119,6 +119,7 @@ mod handlers {
     mod change_visibility;
     mod convert_bool_then;
     mod convert_bool_to_enum;
+    mod convert_char_literal;
     mod convert_closure_to_fn;
     mod convert_comment_block;
     mod convert_comment_from_or_to_doc;
@@ -256,6 +257,7 @@ mod handlers {
             convert_bool_then::convert_bool_then_to_if,
             convert_bool_then::convert_if_to_bool_then,
             convert_bool_to_enum::convert_bool_to_enum,
+            convert_char_literal::convert_char_literal,
             convert_closure_to_fn::convert_closure_to_fn,
             convert_comment_block::convert_comment_block,
             convert_comment_from_or_to_doc::convert_comment_from_or_to_doc,

crates/ide-assists/src/tests/generated.rs

@@ -424,6 +424,19 @@ fn main() {
     )
 }
 
+#[test]
+fn doctest_convert_char_literal() {
+    check_doc_test(
+        "convert_char_literal",
+        r#####"
+const _: char = 'a'$0;
+"#####,
+        r#####"
+const _: char = '\x61';
+"#####,
+    )
+}
+
 #[test]
 fn doctest_convert_closure_to_fn() {
     check_doc_test(