From c58edbff754a21771ab66e914d6320a28cfae80d Mon Sep 17 00:00:00 2001
From: Yingchi Long <i@lyc.dev>
Date: Wed, 24 Apr 2024 18:30:10 +0800
Subject: [PATCH] libnixf: diagnose empty inherit (#457)

---
 libnixf/src/Parse/ParseAttrs.cpp  | 16 ++++++++++++++-
 libnixf/test/Parse/ParseAttrs.cpp | 34 +++++++++++++++++++++++++++++--
 2 files changed, 47 insertions(+), 3 deletions(-)

diff --git a/libnixf/src/Parse/ParseAttrs.cpp b/libnixf/src/Parse/ParseAttrs.cpp
index 206e8ed75..37afc49b3 100644
--- a/libnixf/src/Parse/ParseAttrs.cpp
+++ b/libnixf/src/Parse/ParseAttrs.cpp
@@ -133,11 +133,25 @@ std::shared_ptr<Inherit> Parser::parseInherit() {
     }
     break;
   }
-  if (ExpectResult ER = expect(tok_semi_colon); ER.ok())
+  ExpectResult ER = expect(tok_semi_colon);
+  if (ER.ok())
     consume();
   else
     ER.diag().note(Note::NK_ToMachThis, TokInherit.range())
         << std::string(tok::spelling(tok_kw_inherit));
+
+  // If attrnames are emtpy, this is an emtpy "inherit";
+  if (AttrNames.empty()) {
+    Diagnostic &D =
+        Diags.emplace_back(Diagnostic::DK_EmptyInherit, TokInherit.range());
+    D.tag(DiagnosticTag::Faded);
+    Fix &F = D.fix("remove `inherit` keyword");
+    F.edit(TextEdit::mkRemoval(TokInherit.range()));
+    if (ER.ok()) {
+      // Remove ";" also.
+      F.edit(TextEdit::mkRemoval(ER.tok().range()));
+    }
+  }
   return std::make_shared<Inherit>(
       LexerCursorRange{TokInherit.lCur(), LastToken->rCur()},
       std::move(AttrNames), std::move(Expr));
diff --git a/libnixf/test/Parse/ParseAttrs.cpp b/libnixf/test/Parse/ParseAttrs.cpp
index 555c02abc..45913e1ac 100644
--- a/libnixf/test/Parse/ParseAttrs.cpp
+++ b/libnixf/test/Parse/ParseAttrs.cpp
@@ -275,7 +275,7 @@ TEST(Parser, AttrsBindingInherit) {
   auto AST = nixf::parse(Src, Diags);
 
   ASSERT_TRUE(AST);
-  ASSERT_EQ(Diags.size(), 5);
+  ASSERT_EQ(Diags.size(), 6);
 
   // Check the bindings.
   const auto &B = static_cast<ExprAttrs *>(AST.get())->binds()->bindings();
@@ -421,6 +421,36 @@ TEST(Parser, SyncInherit3) {
   ASSERT_EQ(N.args()[0], "(");
 }
 
+TEST(Parser, InheritEmpty) {
+  auto Src = R"({ inherit; })"sv;
+
+  std::vector<Diagnostic> Diags;
+  auto AST = nixf::parse(Src, Diags);
+
+  ASSERT_TRUE(AST);
+
+  ASSERT_EQ(Diags.size(), 1);
+  auto &D = Diags[0];
+  ASSERT_TRUE(D.range().lCur().isAt(0, 2, 2));
+  ASSERT_TRUE(D.range().rCur().isAt(0, 9, 9));
+
+  // Check the fix.
+  const Fix &F = Diags[0].fixes()[0];
+
+  ASSERT_EQ(F.edits().size(), 2);
+  ASSERT_TRUE(F.edits()[0].isRemoval());
+  ASSERT_EQ(F.edits()[0].oldRange().lCur().line(), 0);
+  ASSERT_EQ(F.edits()[0].oldRange().lCur().column(), 2);
+  ASSERT_EQ(F.edits()[0].oldRange().rCur().line(), 0);
+  ASSERT_EQ(F.edits()[0].oldRange().rCur().column(), 9);
+
+  // Second, remove the semicolon.
+  ASSERT_EQ(F.edits()[1].oldRange().lCur().line(), 0);
+  ASSERT_EQ(F.edits()[1].oldRange().lCur().column(), 9);
+  ASSERT_EQ(F.edits()[1].oldRange().rCur().line(), 0);
+  ASSERT_EQ(F.edits()[1].oldRange().rCur().column(), 10);
+}
+
 TEST(Parser, InheritMissingSemi) {
   auto Src = R"(
 {
@@ -433,7 +463,7 @@ TEST(Parser, InheritMissingSemi) {
 
   ASSERT_TRUE(AST);
 
-  ASSERT_EQ(Diags.size(), 1);
+  ASSERT_EQ(Diags.size(), 2);
   auto &D = Diags[0];
   ASSERT_TRUE(D.range().lCur().isAt(2, 9, 12));
   ASSERT_TRUE(D.range().rCur().isAt(2, 9, 12));