[clangd] UI for completion items that would trigger include insertion.

Summary:
For completion items that would trigger include insertions (i.e. index symbols
that are not #included yet), add a visual indicator "+" before the completion
label. The inserted headers will appear in the completion detail.

Open to suggestions for better visual indicators; "+" was picked because it
seems cleaner than a few other candidates I've tried (*, #, @ ...).

The displayed header would be like a/b/c.h (without quote) or <vector> for system
headers. I didn't add quotation or "#include" because they can take up limited
space and do not provide additional information after users know what the
headers are. I think a header alone should be obvious for users to infer that
this is an include header..

To align indentation, also prepend ' ' to labels of candidates that would not
trigger include insertions (only for completions where index results are
possible).

Vim:
{F6357587}

vscode:
{F6357589}
{F6357591}

Reviewers: sammccall, ilya-biryukov, hokein

Reviewed By: sammccall

Subscribers: MaskRay, jkorous, cfe-commits

Differential Revision: https://reviews.llvm.org/D48163

1 files changed, 7 insertions, 0 deletions

diff --git a/clang-tools-extra/clangd/CodeComplete.h b/clang-tools-extra/clangd/CodeComplete.h
index 4fb19cb1073..f89aad76cfe 100644
--- a/clang-tools-extra/clangd/CodeComplete.h
+++ b/clang-tools-extra/clangd/CodeComplete.h
@@ -60,6 +60,13 @@ struct CodeCompleteOptions {
   /// If more results are available, we set CompletionList.isIncomplete.
   size_t Limit = 0;
 
+  /// A visual indicator to prepend to the completion label to indicate whether
+  /// completion result would trigger an #include insertion or not.
+  struct IncludeInsertionIndicator {
+    std::string Insert = "•";
+    std::string NoInsert = " ";
+  } IncludeIndicator;
+
   // Populated internally by clangd, do not set.
   /// If `Index` is set, it is used to augment the code completion
   /// results.