Add remove_empty_inherit assist

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

@@ -14,6 +14,7 @@ mod add_to_top_level_lambda_param;
 mod convert_to_inherit;
 mod flatten_attrset;
 mod pack_bindings;
+mod remove_empty_inherit;
 
 use crate::{DefDatabase, FileRange, TextEdit, WorkspaceEdit};
 use syntax::ast::{self, AstNode};
@@ -41,6 +42,7 @@ pub(crate) fn assists(db: &dyn DefDatabase, frange: FileRange) -> Vec<Assist> {
         convert_to_inherit::convert_to_inherit,
         flatten_attrset::flatten_attrset,
         pack_bindings::pack_bindings,
+        remove_empty_inherit::remove_empty_inherit,
     ];
 
     let mut ctx = AssistsCtx::new(db, frange);

crates/ide/src/ide/assists/remove_empty_inherit.rs

@@ -0,0 +1,72 @@
+//! Remove an empty `inherit`.
+//!
+//! ```nix
+//! { foo = "bar"; inherit; }
+//! ```
+//! =>
+//! ```nix
+//! { foo = "bar"; }
+//! ```
+use super::{AssistKind, AssistsCtx};
+use crate::TextEdit;
+use syntax::ast::{self, AstNode};
+use syntax::SyntaxKind;
+
+pub(super) fn remove_empty_inherit(ctx: &mut AssistsCtx<'_>) -> Option<()> {
+    let node = ctx.covering_node::<ast::Inherit>()?;
+
+    // There should be no attrs inherited.
+    if node.attrs().next().is_some() {
+        return None;
+    }
+
+    let syntax = node.syntax();
+    let mut range = syntax.text_range();
+    // Also remove trailing SPACEs.
+    if let Some(ws) = syntax
+        .last_token()?
+        .next_token()
+        .filter(|tok| tok.kind() == SyntaxKind::SPACE)
+    {
+        range = range.cover(ws.text_range());
+    }
+
+    ctx.add(
+        "remove_empty_inherit",
+        "Remove the empty `inherit`",
+        AssistKind::QuickFix,
+        vec![TextEdit {
+            delete: range,
+            insert: Default::default(),
+        }],
+    );
+
+    Some(())
+}
+
+#[cfg(test)]
+mod tests {
+    use expect_test::expect;
+
+    define_check_assist!(super::remove_empty_inherit);
+
+    #[test]
+    fn simple() {
+        check("{ inherit;$0 }", expect!["{ }"]);
+        check("{ $0inherit ({ }); }", expect!["{ }"]);
+        check(
+            r#"{ foo = "bar"; inherit$0; }"#,
+            expect![r#"{ foo = "bar"; }"#],
+        );
+        check(r#"let inhe$0rit; in "foo""#, expect![r#"let in "foo""#]);
+        check("let inherit ({ $0foo = 42; }); in 42", expect!["let in 42"]);
+
+        check("{inhe$0rit;}", expect!["{}"]);
+        check("{inherit$0;\n}", expect!["{}"]);
+
+        check_no("{ in$0herit foo; }");
+        check_no("{ inher$0it ({ foo = 42; }) foo; }");
+        check_no(r#"let inherit foo;$0 in foo"#);
+        check_no(r#"let inherit ({ foo =$0 "bar"; }) foo; in foo"#);
+    }
+}