[clangd] Avoid duplicates in findDefinitions response

Summary:
When compile_commands.json contains some source files expressed as
relative paths, we can get duplicate responses to findDefinitions.  The
responses only differ by the URI, which are different versions of the
same file:

    "result": [
        {
            ...
            "uri": "file:///home/emaisin/src/ls-interact/cpp-test/build/../src/first.h"
        },
        {
            ...
            "uri": "file:///home/emaisin/src/ls-interact/cpp-test/src/first.h"
        }
    ]

In getAbsoluteFilePath, we try to obtain the realpath of the FileEntry
by calling tryGetRealPathName.  However, this can fail and return an
empty string.  It may be bug a bug in clang, but in any case we should
fall back to computing it ourselves if it happens.

I changed getAbsoluteFilePath so that if tryGetRealPathName succeeds, we
return right away (a real path is always absolute).  Otherwise, we try
to build an absolute path, as we did before, but we also call
VFS->getRealPath to make sure to get the canonical path (e.g. without
any ".." in it).

Reviewers: malaperle

Subscribers: hokein, ilya-biryukov, ioeric, MaskRay, jkorous, cfe-commits

Differential Revision: https://reviews.llvm.org/D48687

llvm-svn: 339483

1 files changed, 25 insertions, 9 deletions

diff --git a/clang-tools-extra/clangd/SourceCode.cpp b/clang-tools-extra/clangd/SourceCode.cpp
index 88ec2c95683..931ad3c0f20 100644
--- a/clang-tools-extra/clangd/SourceCode.cpp
+++ b/clang-tools-extra/clangd/SourceCode.cpp
@@ -185,18 +185,34 @@ std::vector<TextEdit> replacementsToEdits(StringRef Code,
   return Edits;
 }
 
-llvm::Optional<std::string>
-getAbsoluteFilePath(const FileEntry *F, const SourceManager &SourceMgr) {
-  SmallString<64> FilePath = F->tryGetRealPathName();
-  if (FilePath.empty())
-    FilePath = F->getName();
-  if (!llvm::sys::path::is_absolute(FilePath)) {
-    if (!SourceMgr.getFileManager().makeAbsolutePath(FilePath)) {
-      log("Could not turn relative path to absolute: {0}", FilePath);
+llvm::Optional<std::string> getRealPath(const FileEntry *F,
+                                        const SourceManager &SourceMgr) {
+  // Ideally, we get the real path from the FileEntry object.
+  SmallString<128> FilePath = F->tryGetRealPathName();
+  if (!FilePath.empty()) {
+    return FilePath.str().str();
+  }
+
+  // Otherwise, we try to compute ourselves.
+  vlog("FileEntry for {0} did not contain the real path.", F->getName());
+
+  llvm::SmallString<128> Path = F->getName();
+
+  if (!llvm::sys::path::is_absolute(Path)) {
+    if (!SourceMgr.getFileManager().makeAbsolutePath(Path)) {
+      log("Could not turn relative path to absolute: {0}", Path);
       return llvm::None;
     }
   }
-  return FilePath.str().str();
+
+  llvm::SmallString<128> RealPath;
+  if (SourceMgr.getFileManager().getVirtualFileSystem()->getRealPath(
+          Path, RealPath)) {
+    log("Could not compute real path: {0}", Path);
+    return Path.str().str();
+  }
+
+  return RealPath.str().str();
 }
 
 TextEdit toTextEdit(const FixItHint &FixIt, const SourceManager &M,