[Clangd] Support Authority-less URIs

Clangd strips URIs by removing the file:// part but some clients can send file:
which is also valid according to RFC 3896. For example, if a client sends
file:///home/user, it gets converted to /home/user but if a client sends
file:/home/user, it is left untouched and problems arise.

Patch by Marc-Andre Laperle!

Differential Revision: https://reviews.llvm.org/D32234

llvm-svn: 300990

clang-tools-extra/clangd/Protocol.cpp

@@ -25,6 +25,8 @@ URI URI::fromUri(llvm::StringRef uri) {
   URI Result;
   Result.uri = uri;
   uri.consume_front("file://");
+  // Also trim authority-less URIs
+  uri.consume_front("file:");
   // For Windows paths e.g. /X:
   if (uri.size() > 2 && uri[0] == '/' && uri[2] == ':')
     uri.consume_front("/");

clang-tools-extra/test/clangd/completion.test

@@ -20,6 +20,16 @@ Content-Length: 148
 # CHECK-DAG: {"label":"bb","kind":5}
 # CHECK-DAG: {"label":"ccc","kind":5}
 # CHECK: ]}
+Content-Length: 146
+
+{"jsonrpc":"2.0","id":1,"method":"textDocument/completion","params":{"textDocument":{"uri":"file:/main.cpp"},"position":{"line":3,"character":5}}}
+# Test authority-less URI
+#
+# CHECK: {"jsonrpc":"2.0","id":1,"result":[
+# CHECK-DAG: {"label":"a","kind":5}
+# CHECK-DAG: {"label":"bb","kind":5}
+# CHECK-DAG: {"label":"ccc","kind":5}
+# CHECK: ]}
 Content-Length: 44
 
 {"jsonrpc":"2.0","id":3,"method":"shutdown"}