[clang-doc] create namespace names according to their paths (llvm#162886)

Namespace filenames didn't consider their paths, so foo::tools would use
the same file as bar::tools. Now we consider their paths to avoid that
problem.

Author: evelez7

clang-tools-extra/clang-doc/JSONGenerator.cpp

@@ -584,12 +584,20 @@ static SmallString<16> determineFileName(Info *I, SmallString<128> &Path) {
     FileName = RecordSymbolInfo->MangledName;
   } else if (I->USR == GlobalNamespaceID)
     FileName = "index";
-  else
+  else if (I->IT == InfoType::IT_namespace) {
+    for (const auto &NS : I->Namespace) {
+      FileName += NS.Name;
+      FileName += "_";
+    }
+    FileName += I->Name;
+  } else
     FileName = I->Name;
   sys::path::append(Path, FileName + ".json");
   return FileName;
 }
 
+// FIXME: Revert back to creating nested directories for namespaces instead of
+// putting everything in a flat directory structure.
 Error JSONGenerator::generateDocs(
     StringRef RootDir, llvm::StringMap<std::unique_ptr<doc::Info>> Infos,
     const ClangDocContext &CDCtx) {

clang-tools-extra/test/clang-doc/json/multiple-namespaces.cpp

@@ -0,0 +1,20 @@
+// RUN: rm -rf %t && mkdir -p %t
+// RUN: clang-doc --output=%t --format=json --executor=standalone %s
+// RUN: FileCheck %s < %t/json/foo_tools.json --check-prefix=CHECK-FOO
+// RUN: FileCheck %s < %t/json/bar_tools.json --check-prefix=CHECK-BAR
+
+namespace foo {
+  namespace tools {
+    class FooTools {};
+  } // namespace tools
+} // namespace foo
+
+namespace bar {
+  namespace tools {
+    class BarTools {};
+  } // namespace tools
+} // namespace bar
+
+// CHECK-FOO: "Name": "tools"
+
+// CHECK-BAR: "Name": "tools"

clang-tools-extra/test/clang-doc/json/nested-namespace.cpp

@@ -1,7 +1,7 @@
 // RUN: rm -rf %t && mkdir -p %t
 // RUN: clang-doc --output=%t --format=json --executor=standalone %s
 // RUN: FileCheck %s < %t/json/nested.json --check-prefix=NESTED
-// RUN: FileCheck %s < %t/json/inner.json --check-prefix=INNER
+// RUN: FileCheck %s < %t/json/nested_inner.json --check-prefix=INNER
 
 namespace nested {
   int Global;