[clangd] NFC: Improve Dex Iterators debugging traits

[kbobyrev]

Summary

This patch improves dex::Iterator string representation by incorporating the information about the element which is currently being pointed to by the DocumentIterator.

[ioeric]

clang-tools-extra/clangd/index/dex/Iterator.h

102

nit: I think *IDX* might look a bit nicer. But up to you :)

[kbobyrev]

Improved wording to prevent confusion: no more IDX (which is the one pointed to by the iterator) and IDN; just mention that the element being pointed to is the one enclosed in {} braces.

clang-tools-extra/clangd/index/dex/Iterator.h

public:
 
   /// Prints a convenient human-readable iterator representation by recursively
   /// dumping iterators in the following format:
   ///
   /// (Type Child1 Child2 ...)
   ///
   /// Where Type is the iterator type representation: "&" for And, "|" for Or,
   /// ChildN is N-th iterator child. Raw iterators over PostingList are
-  /// represented as "[ID1, ID2, ...]" where IDN is N-th PostingList entry.
+  /// represented as "[ID1, ID2, ..., {IDX}, ... END]" where IDN is N-th
+  /// PostingList entry and IDX is the one currently being pointed to by the
+  /// corresponding iterator.
   friend llvm::raw_ostream &operator<<(llvm::raw_ostream &OS,
                                        const Iterator &Iterator) {
     return Iterator.dump(OS);
   }
 
 private:
   virtual llvm::raw_ostream &dump(llvm::raw_ostream &OS) const = 0;
 };

clang-tools-extra/clangd/index/dex/Iterator.cpp

public:
   DocID peek() const override {
     assert(!reachedEnd() && "DocumentIterator can't call peek() at the end.");
     return *Index;
   }
 
   llvm::raw_ostream &dump(llvm::raw_ostream &OS) const override {
     OS << '[';
     auto Separator = "";
-    for (const auto &ID : Documents) {
-      OS << Separator << ID;
+    for (auto It = std::begin(Documents); It != std::end(Documents); ++It) {
+      OS << Separator;
+      if (It == Index)
+        OS << '{' << *It << '}';
+      else
+        OS << *It;
       Separator = ", ";
     }
+    OS << Separator;
+    if (Index == std::end(Documents))
+      OS << "{END}";
+    else
+      OS << "END";
     OS << ']';
     return OS;
   }
 
 private:
   PostingListRef Documents;
   PostingListRef::const_iterator Index;
 };

clang-tools-extra/unittests/clangd/DexIndexTests.cpp

 TEST(DexIndexIterators, StringRepresentation) {
   const PostingList L0 = {4, 7, 8, 20, 42, 100};
   const PostingList L1 = {1, 3, 5, 8, 9};
   const PostingList L2 = {1, 5, 7, 9};
   const PostingList L3 = {0, 5};
   const PostingList L4 = {0, 1, 5};
   const PostingList L5;
 
-  EXPECT_EQ(llvm::to_string(*(create(L0))), "[4, 7, 8, 20, 42, 100]");
+  EXPECT_EQ(llvm::to_string(*(create(L0))), "[{4}, 7, 8, 20, 42, 100, END]");
 
   auto Nested = createAnd(createAnd(create(L1), create(L2)),
                           createOr(create(L3), create(L4), create(L5)));
 
   EXPECT_EQ(llvm::to_string(*Nested),
-            "(& (& [1, 3, 5, 8, 9] [1, 5, 7, 9]) (| [0, 5] [0, 1, 5] []))");
+            "(& (& [{1}, 3, 5, 8, 9, END] [{1}, 5, 7, 9, END]) (| [0, {5}, "
+            "END] [0, {1}, 5, END] [{END}]))");
 }
 
 TEST(DexIndexIterators, Limit) {
   const PostingList L0 = {4, 7, 8, 20, 42, 100};
   const PostingList L1 = {1, 3, 5, 8, 9};
   const PostingList L2 = {1, 5, 7, 9};
   const PostingList L3 = {0, 5};
   const PostingList L4 = {0, 1, 5};