Add remove_unused_with assist

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

@@ -21,6 +21,7 @@ mod pack_bindings;
 mod remove_empty_inherit;
 mod remove_empty_let_in;
 mod remove_unused_binding;
+mod remove_unused_with;
 mod rewrite_string;
 
 use crate::{DefDatabase, FileRange, TextEdit, WorkspaceEdit};
@@ -53,6 +54,7 @@ pub(crate) fn assists(db: &dyn DefDatabase, frange: FileRange) -> Vec<Assist> {
         remove_empty_inherit::remove_empty_inherit,
         remove_empty_let_in::remove_empty_let_in,
         remove_unused_binding::remove_unused_binding,
+        remove_unused_with::remove_unused_with,
         rewrite_string::quote_attr,
         rewrite_string::rewrite_indented_to_string,
         rewrite_string::rewrite_string_to_indented,

crates/ide/src/ide/assists/remove_unused_with.rs

@@ -0,0 +1,79 @@
+//! Remove an unused `with ...`.
+//!
+//! ```nix
+//! foo = with pkgs; [ pkgs.bar ];
+//! ```
+//! =>
+//! ```nix
+//! foo = [ pkgs.bar ];
+//! ```
+use super::{AssistKind, AssistsCtx};
+use crate::DiagnosticKind::UnusedWith;
+use crate::TextEdit;
+use syntax::ast;
+
+pub(super) fn remove_unused_with(ctx: &mut AssistsCtx<'_>) -> Option<()> {
+    let cursor_with = ctx.covering_node::<ast::With>()?;
+    let with_range = cursor_with.with_token()?.text_range();
+
+    let file = ctx.frange.file_id;
+    let check = ctx.db.liveness_check(file);
+    let diags = check.as_ref().to_diagnostics(ctx.db, file);
+
+    let no_relevant_diags = diags
+        .filter(|d| d.kind == UnusedWith && d.range.intersect(with_range).is_some())
+        .count()
+        == 0;
+
+    if no_relevant_diags {
+        return None;
+    }
+
+    let semicolon_token = cursor_with.semicolon_token()?;
+    let trivia_range = std::iter::successors(semicolon_token.next_token(), |tok| tok.next_token())
+        .take_while(|tok| tok.kind().is_trivia())
+        .last()
+        .unwrap_or(semicolon_token);
+
+    ctx.add(
+        "remove_unused_with",
+        "Remove unused with",
+        AssistKind::QuickFix,
+        vec![TextEdit {
+            delete: with_range.cover(trivia_range.text_range()),
+            insert: Default::default(),
+        }],
+    );
+
+    Some(())
+}
+
+#[cfg(test)]
+mod tests {
+    use expect_test::expect;
+
+    define_check_assist!(super::remove_unused_with);
+
+    #[test]
+    fn in_use_with() {
+        check_no("a: $0with lib; bar");
+    }
+
+    #[test]
+    fn unused_with() {
+        // Simple
+        check("a: $0with 1;a", expect!["a: a"]);
+
+        // With trivia
+        check("a: $0with /* trivia */ 1;   a", expect!["a: a"]);
+
+        // With array
+        check("a: $0with [ 1 ];   a", expect!["a: a"]);
+
+        // 1st of multiple
+        check("a: $0with 1;     with 2; a", expect!["a: with 2; a"]);
+
+        // 2nd of multiple
+        check("a: with 1; $0with 2;     a", expect!["a: with 1; a"]);
+    }
+}

docs/code_actions.md

@@ -142,6 +142,18 @@ let
 in {}
 ```
 
+### `remove_unused_with`
+
+Remove an unused `with ...`.
+
+```nix
+foo = with pkgs; [ pkgs.bar ];
+```
+=>
+```nix
+foo = [ pkgs.bar ];
+```
+
 ### `rewrite_string_to_indented` and `rewrite_indented_to_string`
 
 Rewrite between double quoted strings and indented strings