[PATCH] D134137: [clangd] Return earlier when snippet is empty

[Tom Praschan via Phabricator via cfe-commits]

tom-anders created this revision.
Herald added subscribers: kadircet, arphaman.
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tom-anders requested review of this revision.
Herald added subscribers: cfe-commits, MaskRay, ilya-biryukov.
Herald added a project: clang-tools-extra.

Fixes github.com/clangd/clangd/issues/1216

If the Snippet string is empty, Snippet.front() would trigger a crash.
Move the Snippet->empty() check up a few lines to avoid this. Should not
break any existing behavior.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D134137

Files:
  clang-tools-extra/clangd/CodeComplete.cpp
  clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp


Index: clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp
===================================================================
--- clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp
+++ clang-tools-extra/clangd/unittests/CodeCompleteTests.cpp
@@ -1014,6 +1014,23 @@
   EXPECT_THAT(Results.Completions, Not(Contains(labeled("clang::"))));
 }
 
+TEST(CompletionTests, EmptySnippetDoesNotCrash) {
+    // See https://github.com/clangd/clangd/issues/1216
+    auto Results = completions(R"cpp(
+        int main() {
+          auto w = [&](auto &&f) { return f(f); };
+          auto f = w([&](auto &&f) {
+            return [&](auto &&n) {
+              if (n == 0) {
+                return 1;
+              }
+              return n * ^(f)(n - 1);
+            };
+          })(10);
+        }
+    )cpp");
+}
+
 TEST(CompletionTest, BacktrackCrashes) {
   // Sema calls code completion callbacks twice in these cases.
   auto Results = completions(R"cpp(
Index: clang-tools-extra/clangd/CodeComplete.cpp
===================================================================
--- clang-tools-extra/clangd/CodeComplete.cpp
+++ clang-tools-extra/clangd/CodeComplete.cpp
@@ -491,6 +491,9 @@
       // we need to complete 'forward<$1>($0)'.
       return "($0)";
 
+    if (Snippet->empty())
+      return "";
+
     bool MayHaveArgList = Completion.Kind == CompletionItemKind::Function ||
                           Completion.Kind == CompletionItemKind::Method ||
                           Completion.Kind == CompletionItemKind::Constructor ||
@@ -529,8 +532,6 @@
       return *Snippet;
 
     // Replace argument snippets with a simplified pattern.
-    if (Snippet->empty())
-      return "";
     if (MayHaveArgList) {
       // Functions snippets can be of 2 types:
       // - containing only function arguments, e.g.


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