[clangd] Implement textDocument/hover

Summary: Implemention of textDocument/hover as described in LSP definition.

This patch adds a basic Hover implementation.  When hovering a variable,
function, method or namespace, clangd will return a text containing the
declaration's scope, as well as the declaration of the hovered entity.
For example, for a variable:

  Declared in class Foo::Bar

  int hello = 2

For macros, the macro definition is returned.

This patch doesn't include:

- markdown support (the client I use doesn't support it yet)
- range support (optional in the Hover response)
- comments associated to variables/functions/classes

They are kept as future work to keep this patch simpler.

I added tests in XRefsTests.cpp.  hover.test contains one simple
smoketest to make sure the feature works from a black box perspective.

Reviewers: malaperle, krasimir, bkramer, ilya-biryukov

Subscribers: sammccall, mgrang, klimek, rwols, ilya-biryukov, arphaman, cfe-commits

Differential Revision: https://reviews.llvm.org/D35894

Signed-off-by: Simon Marchi <simon.marchi@ericsson.com>
Signed-off-by: William Enright <william.enright@polymtl.ca>
llvm-svn: 325395

1 files changed, 21 insertions, 0 deletions

diff --git a/clang-tools-extra/clangd/Protocol.h b/clang-tools-extra/clangd/Protocol.h
index 3007dc368a4..bdbbf62f7ab 100644
--- a/clang-tools-extra/clangd/Protocol.h
+++ b/clang-tools-extra/clangd/Protocol.h
@@ -480,6 +480,27 @@ struct TextDocumentPositionParams {
 };
 bool fromJSON(const json::Expr &, TextDocumentPositionParams &);
 
+enum class MarkupKind {
+  PlainText,
+  Markdown,
+};
+
+struct MarkupContent {
+  MarkupKind Kind = MarkupKind::PlainText;
+  std::string Value;
+};
+json::Expr toJSON(const MarkupContent &MC);
+
+struct Hover {
+  /// The hover's content
+  MarkupContent Contents;
+
+  /// An optional range is a range inside a text document
+  /// that is used to visualize a hover, e.g. by changing the background color.
+  llvm::Optional<Range> Range;
+};
+json::Expr toJSON(const Hover &H);
+
 /// The kind of a completion entry.
 enum class CompletionItemKind {
   Missing = 0,