ide: code action isnull -> is null, notnull -> is not null

crates/squawk_ide/src/code_actions/mod.rs

@@ -27,6 +27,7 @@ mod rewrite_is_normalized_as_function_call;
 mod rewrite_leading_from;
 mod rewrite_normalize_as_function_call;
 mod rewrite_not_equals_operator;
+mod rewrite_null_predicate;
 mod rewrite_overlaps_as_function_call;
 mod rewrite_overlay_as_function_call;
 mod rewrite_pattern_matching_as_operators;
@@ -72,6 +73,7 @@ use rewrite_is_normalized_as_function_call::rewrite_is_normalized_as_function_ca
 use rewrite_leading_from::rewrite_leading_from;
 use rewrite_normalize_as_function_call::rewrite_normalize_as_function_call;
 use rewrite_not_equals_operator::rewrite_not_equals_operator;
+use rewrite_null_predicate::rewrite_null_predicate;
 use rewrite_overlaps_as_function_call::rewrite_overlaps_as_function_call;
 use rewrite_overlay_as_function_call::rewrite_overlay_as_function_call;
 use rewrite_pattern_matching_as_operators::rewrite_pattern_matching_as_operators;
@@ -127,6 +129,7 @@ pub fn code_actions(db: &dyn Db, position: InFile<TextSize>) -> Option<Vec<CodeA
     rewrite_double_colon_to_cast(db, position, &mut actions);
     rewrite_between_as_binary_expression(db, position, &mut actions);
     rewrite_not_equals_operator(db, position, &mut actions);
+    rewrite_null_predicate(db, position, &mut actions);
     rewrite_timestamp_type(db, position, &mut actions);
     rewrite_unnest_as_rows_from(db, position, &mut actions);
     rewrite_rows_from_as_unnest(db, position, &mut actions);

crates/squawk_ide/src/code_actions/rewrite_null_predicate.rs

@@ -0,0 +1,72 @@
+use rowan::TextSize;
+use salsa::Database as Db;
+use squawk_linter::Edit;
+use squawk_syntax::ast::{self, AstNode, PostfixOp};
+
+use crate::{file::InFile, offsets::token_from_offset};
+
+use super::{ActionKind, CodeAction};
+
+pub(super) fn rewrite_null_predicate(
+    db: &dyn Db,
+    position: InFile<TextSize>,
+    actions: &mut Vec<CodeAction>,
+) -> Option<()> {
+    let token = token_from_offset(db, position)?;
+    let postfix_expr = token.parent_ancestors().find_map(ast::PostfixExpr::cast)?;
+
+    let (op_token, replacement, title) = match postfix_expr.op()? {
+        PostfixOp::IsNull(token) => (token, "is null", "Rewrite as `IS NULL`"),
+        PostfixOp::NotNull(token) => (token, "is not null", "Rewrite as `IS NOT NULL`"),
+        _ => return None,
+    };
+
+    actions.push(CodeAction {
+        title: title.to_owned(),
+        edits: vec![Edit::replace(op_token.text_range(), replacement.to_owned())],
+        kind: ActionKind::RefactorRewrite,
+    });
+
+    Some(())
+}
+
+#[cfg(test)]
+mod test {
+    use insta::assert_snapshot;
+
+    use crate::code_actions::test_utils::{apply_code_action, code_action_not_applicable};
+
+    use super::rewrite_null_predicate;
+
+    #[test]
+    fn rewrites_isnull() {
+        assert_snapshot!(
+            apply_code_action(rewrite_null_predicate, "select x is$0null from t;"),
+            @"select x is null from t;"
+        );
+    }
+
+    #[test]
+    fn rewrites_notnull() {
+        assert_snapshot!(
+            apply_code_action(rewrite_null_predicate, "select x not$0null from t;"),
+            @"select x is not null from t;"
+        );
+    }
+
+    #[test]
+    fn applies_when_cursor_is_on_the_value() {
+        assert_snapshot!(
+            apply_code_action(rewrite_null_predicate, "select val$0ue isnull from t;"),
+            @"select value is null from t;"
+        );
+    }
+
+    #[test]
+    fn is_not_applicable_outside_null_predicate() {
+        assert!(code_action_not_applicable(
+            rewrite_null_predicate,
+            "select val$0ue from t;"
+        ));
+    }
+}