Add add_to_top_level_lambda_param assist

crates/ide/src/ide/assists/add_to_top_level_lambda_param.rs

@@ -0,0 +1,91 @@
+//! Add an undefined name to the top-level lambda.
+//!
+//! ```nix
+//! { foo }: foo + bar
+//! ```
+//! =>
+//! ```nix
+//! { foo, bar }: foo + bar
+//! ```
+use super::{AssistKind, AssistsCtx};
+use crate::TextEdit;
+use syntax::ast::{self, AstNode};
+use syntax::{SyntaxNodePtr, TextRange, TextSize};
+
+pub(super) fn add_to_top_level_lambda_param(ctx: &mut AssistsCtx<'_>) -> Option<()> {
+    let node = ctx.covering_node::<ast::Ref>()?;
+    let name = node.token()?;
+    let name = name.text();
+
+    // The whole file should be a lambda.
+    let pat = ast::Lambda::cast(ctx.ast.syntax().first_child()?)?
+        .param()?
+        .pat()?;
+
+    // Name should be undefined.
+    let expr = ctx
+        .db
+        .source_map(ctx.frange.file_id)
+        .expr_for_node(SyntaxNodePtr::new(node.syntax()))?;
+    if ctx
+        .db
+        .name_resolution(ctx.frange.file_id)
+        .get(expr)
+        .is_some()
+    {
+        return None;
+    };
+
+    let (pos, insert) = if let Some(field) = pat.fields().last() {
+        let field = field.syntax();
+        let mut pos = field.text_range().end();
+        // Insert before the space if the field ends with a space.
+        if matches!(field.last_token(), Some(tok) if tok.text().ends_with(' ')) {
+            pos -= TextSize::from(1);
+        }
+        (pos, format!(", {name}"))
+    } else if let Some(ellipsis) = pat.ellipsis_token() {
+        (ellipsis.text_range().start(), format!("{name}, "))
+    } else if let Some(curly) = pat.r_curly_token() {
+        (curly.text_range().start(), format!("{name} "))
+    } else {
+        (pat.syntax().text_range().start(), name.into())
+    };
+
+    ctx.add(
+        "add_to_top_level_lambda_param",
+        format!("Add `{name}` to the top-level lambda parameter"),
+        AssistKind::QuickFix,
+        vec![TextEdit {
+            delete: TextRange::new(pos, pos),
+            insert: insert.into(),
+        }],
+    );
+
+    Some(())
+}
+
+#[cfg(test)]
+mod tests {
+    use expect_test::expect;
+
+    define_check_assist!(super::add_to_top_level_lambda_param);
+
+    #[test]
+    fn simple() {
+        check("{ }: foo$0", expect!["{ foo }: foo"]);
+        check("{}: foo$0", expect!["{foo }: foo"]);
+        check("{ foo }: b$0ar", expect!["{ foo, bar }: bar"]);
+        check("{foo}: $0bar", expect!["{foo, bar}: bar"]);
+        check("{ ... }: foo$0", expect!["{ foo, ... }: foo"]);
+        check("{...}: foo$0", expect!["{foo, ...}: foo"]);
+        check("{foo, ...}: $0bar", expect!["{foo, bar, ...}: bar"]);
+        check("{foo,...}: $0bar", expect!["{foo, bar,...}: bar"]);
+
+        check_no("{ foo }: fo$0o");
+        check_no("{ }: foo.$0bar");
+        check_no("{ }: let foo = bar; in f$0oo");
+        check_no("{ bar }: { fo$0o = bar; }");
+        check_no("bar: fo$0o");
+    }
+}

crates/ide/src/ide/assists/mod.rs

@@ -10,6 +10,7 @@ macro_rules! define_check_assist {
     };
 }
 
+mod add_to_top_level_lambda_param;
 mod convert_to_inherit;
 mod flatten_attrset;
 mod pack_bindings;
@@ -30,11 +31,13 @@ pub struct Assist {
 
 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub enum AssistKind {
+    QuickFix,
     RefactorRewrite,
 }
 
 pub(crate) fn assists(db: &dyn DefDatabase, frange: FileRange) -> Vec<Assist> {
     let handlers = [
+        add_to_top_level_lambda_param::add_to_top_level_lambda_param,
         convert_to_inherit::convert_to_inherit,
         flatten_attrset::flatten_attrset,
         pack_bindings::pack_bindings,

crates/nil/src/convert.rs

@@ -306,6 +306,7 @@ pub(crate) fn to_code_action(vfs: &Vfs, assist: Assist) -> CodeActionOrCommand {
     CodeActionOrCommand::CodeAction(CodeAction {
         title: assist.label,
         kind: Some(match assist.kind {
+            AssistKind::QuickFix => CodeActionKind::QUICKFIX,
             AssistKind::RefactorRewrite => CodeActionKind::REFACTOR_REWRITE,
         }),
         diagnostics: None,