[clangd] Improve global code completion when scope specifier is unresolved.

Summary:
Suppose `clangd::` is unresolved in the following example. Currently,
we simply use "clangd::" as the query scope. We can do better by combining with
accessible scopes in the context. The query scopes can be `{clangd::, clang::clangd::}`.
```
namespace clang { clangd::^ }

```

Reviewers: ilya-biryukov, sammccall, hokein, kadircet

Reviewed By: kadircet

Subscribers: MaskRay, jkorous, arphaman, kadircet, jdoerfert, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D58448

llvm-svn: 354963

1 files changed, 33 insertions, 2 deletions

diff --git a/clang-tools-extra/unittests/clangd/CodeCompleteTests.cpp b/clang-tools-extra/unittests/clangd/CodeCompleteTests.cpp
index df7c8ef19d6..16d8efcf810 100644
--- a/clang-tools-extra/unittests/clangd/CodeCompleteTests.cpp
+++ b/clang-tools-extra/unittests/clangd/CodeCompleteTests.cpp
@@ -1095,8 +1095,10 @@ TEST(CompletionTest, UnresolvedQualifierIdQuery) {
       } // namespace ns
   )cpp");
 
-  EXPECT_THAT(Requests, ElementsAre(Field(&FuzzyFindRequest::Scopes,
-                                          UnorderedElementsAre("bar::"))));
+  EXPECT_THAT(Requests,
+              ElementsAre(Field(
+                  &FuzzyFindRequest::Scopes,
+                  UnorderedElementsAre("a::bar::", "ns::bar::", "bar::"))));
 }
 
 TEST(CompletionTest, UnresolvedNestedQualifierIdQuery) {
@@ -2335,6 +2337,35 @@ TEST(CompletionTest, UsingDecl) {
                                 Kind(CompletionItemKind::Reference))));
 }
 
+TEST(CompletionTest, ScopeIsUnresolved) {
+  clangd::CodeCompleteOptions Opts = {};
+  Opts.AllScopes = true;
+
+  auto Results = completions(R"cpp(
+    namespace a {
+    void f() { b::X^ }
+    }
+  )cpp",
+                             {cls("a::b::XYZ")}, Opts);
+  EXPECT_THAT(Results.Completions,
+              UnorderedElementsAre(AllOf(Qualifier(""), Named("XYZ"))));
+}
+
+TEST(CompletionTest, NestedScopeIsUnresolved) {
+  clangd::CodeCompleteOptions Opts = {};
+  Opts.AllScopes = true;
+
+  auto Results = completions(R"cpp(
+    namespace a {
+    namespace b {}
+    void f() { b::c::X^ }
+    }
+  )cpp",
+                             {cls("a::b::c::XYZ")}, Opts);
+  EXPECT_THAT(Results.Completions,
+              UnorderedElementsAre(AllOf(Qualifier(""), Named("XYZ"))));
+}
+
 } // namespace
 } // namespace clangd
 } // namespace clang