[CodeComplete] Add an option to omit results from the preamble.

Summary:
Enumerating the contents of a namespace or global scope will omit any
decls that aren't already loaded, instead of deserializing them from the
PCH.

This allows a fast hybrid code completion where symbols from headers are
provided by an external index. (Sema already exposes the information
needed to do a reasonabl job of filtering them).
Clangd plans to implement this hybrid.

This option is just a hint - callers still need to postfilter results if
they want to *avoid* completing decls outside the main file.

Reviewers: bkramer, ilya-biryukov

Subscribers: cfe-commits

Differential Revision: https://reviews.llvm.org/D41989

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@322371 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 21 insertions, 0 deletions

diff --git a/test/Index/complete-pch-skip.cpp b/test/Index/complete-pch-skip.cpp
new file mode 100644
index 0000000000..866976f990
--- /dev/null
+++ b/test/Index/complete-pch-skip.cpp
@@ -0,0 +1,18 @@
+namespace ns {
+int bar;
+}
+
+int main() { return ns:: }
+
+// RUN: echo "namespace ns { int foo; }" > %t.h
+// RUN: c-index-test -write-pch %t.h.pch -x c++-header %t.h
+//
+// RUN: c-index-test -code-completion-at=%s:5:26 -include %t.h %s | FileCheck -check-prefix=WITH-PCH %s
+// WITH-PCH: {TypedText bar}
+// WITH-PCH: {TypedText foo}
+
+// RUN: env CINDEXTEST_COMPLETION_SKIP_PREAMBLE=1 c-index-test -code-completion-at=%s:5:26 -include %t.h %s | FileCheck -check-prefix=SKIP-PCH %s
+// SKIP-PCH-NOT: foo
+// SKIP-PCH: {TypedText bar}
+// SKIP-PCH-NOT: foo
+
diff --git a/test/Index/complete-pch-skip.h b/test/Index/complete-pch-skip.h
new file mode 100644
index 0000000000..f7422af773
--- /dev/null
+++ b/test/Index/complete-pch-skip.h
@@ -0,0 +1,3 @@
+namespace ns {
+int foo;
+}