Supports adding insertion around non-insertion replacements.

Summary:
Extend `tooling::Replacements::add()` to support adding order-independent replacements.

Two replacements are considered order-independent if one of the following conditions is true:
  - They do not overlap. (This is already supported.)
  - One replacement is insertion, and the other is a replacement with
    length > 0, and the insertion is adjecent to but not contained in the
    other replacement. In this case, the replacement should always change
    the original code instead of the inserted text.

Reviewers: klimek, djasper

Subscribers: cfe-commits, klimek

Differential Revision: https://reviews.llvm.org/D24515

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@281457 91177308-0d34-0410-b5e6-96231b3b80d8

include/clang/Tooling/Core/Replacement.h

@@ -158,14 +158,18 @@ class Replacements {
 
   /// \brief Adds a new replacement \p R to the current set of replacements.
   /// \p R must have the same file path as all existing replacements.
-  /// Returns true if the replacement is successfully inserted; otherwise,
+  /// Returns `success` if the replacement is successfully inserted; otherwise,
   /// it returns an llvm::Error, i.e. there is a conflict between R and the
-  /// existing replacements or R's file path is different from the filepath of
-  /// existing replacements. Callers must explicitly check the Error returned.
-  /// This prevents users from adding order-dependent replacements. To control
-  /// the order in which order-dependent replacements are applied, use
-  /// merge({R}) with R referring to the changed code after applying all
-  /// existing replacements.
+  /// existing replacements (i.e. they are order-dependent) or R's file path is
+  /// different from the filepath of existing replacements. Callers must
+  /// explicitly check the Error returned. This prevents users from adding
+  /// order-dependent replacements. To control the order in which
+  /// order-dependent replacements are applied, use merge({R}) with R referring
+  /// to the changed code after applying all existing replacements.
+  /// Two replacements are considered order-independent if they:
+  ///   - don't overlap (being directly adjacent is fine) and
+  ///   - aren't both inserts at the same code location (would be
+  ///     order-dependent).
   /// Replacements with offset UINT_MAX are special - we do not detect conflicts
   /// for such replacements since users may add them intentionally as a special
   /// category of replacements.

lib/Tooling/Core/Replacement.cpp

@@ -137,6 +137,14 @@ void Replacement::setFromSourceRange(const SourceManager &Sources,
                         ReplacementText);
 }
 
+llvm::Error makeConflictReplacementsError(const Replacement &New,
+                                          const Replacement &Existing) {
+  return llvm::make_error<llvm::StringError>(
+      "New replacement:\n" + New.toString() +
+          "\nconflicts with existing replacement:\n" + Existing.toString(),
+      llvm::inconvertibleErrorCode());
+}
+
 llvm::Error Replacements::add(const Replacement &R) {
   // Check the file path.
   if (!Replaces.empty() && R.getFilePath() != Replaces.begin()->getFilePath())
@@ -163,11 +171,22 @@ llvm::Error Replacements::add(const Replacement &R) {
   // entries that start at the end can still be conflicting if R is an
   // insertion.
   auto I = Replaces.lower_bound(AtEnd);
-  // If it starts at the same offset as R (can only happen if R is an
-  // insertion), we have a conflict.  In that case, increase I to fall through
-  // to the conflict check.
-  if (I != Replaces.end() && R.getOffset() == I->getOffset())
-    ++I;
+  // If `I` starts at the same offset as `R`, `R` must be an insertion.
+  if (I != Replaces.end() && R.getOffset() == I->getOffset()) {
+    assert(R.getLength() == 0);
+    // `I` is also an insertion, `R` and `I` conflict.
+    if (I->getLength() == 0)
+      return makeConflictReplacementsError(R, *I);
+    // Insertion `R` is adjacent to a non-insertion replacement `I`, so they
+    // are order-independent. It is safe to assume that `R` will not conflict
+    // with any replacement before `I` since all replacements before `I` must
+    // either end before `R` or end at `R` but has length > 0 (if the
+    // replacement before `I` is an insertion at `R`, it would have been `I`
+    // since it is a lower bound of `AtEnd` and ordered before the current `I`
+    // in the set).
+    Replaces.insert(R);
+    return llvm::Error::success();
+  }
 
   // I is the smallest iterator whose entry cannot overlap.
   // If that is begin(), there are no overlaps.
@@ -178,16 +197,19 @@ llvm::Error Replacements::add(const Replacement &R) {
   --I;
   // If the previous entry does not overlap, we know that entries before it
   // can also not overlap.
-  if (R.getOffset() != I->getOffset() &&
-      !Range(R.getOffset(), R.getLength())
+  if (!Range(R.getOffset(), R.getLength())
            .overlapsWith(Range(I->getOffset(), I->getLength()))) {
+    // If `R` and `I` do not have the same offset, it is safe to add `R` since
+    // it must come after `I`. Otherwise:
+    //   - If `R` is an insertion, `I` must not be an insertion since it would
+    //   have come after `AtEnd` if it has length 0.
+    //   - If `R` is not an insertion, `I` must be an insertion; otherwise, `R`
+    //   and `I` would have overlapped.
+    // In either case, we can safely insert `R`.
     Replaces.insert(R);
     return llvm::Error::success();
   }
-  return llvm::make_error<llvm::StringError>(
-      "New replacement:\n" + R.toString() +
-          "\nconflicts with existing replacement:\n" + I->toString(),
-      llvm::inconvertibleErrorCode());
+  return makeConflictReplacementsError(R, *I);
 }
 
 namespace {

unittests/Tooling/RefactoringTest.cpp

@@ -115,15 +115,16 @@ TEST_F(ReplacementTest, FailAddReplacements) {
   llvm::consumeError(std::move(Err));
 }
 
-TEST_F(ReplacementTest, FailAddOverlappingInsertions) {
+TEST_F(ReplacementTest, AddAdjacentInsertionAndReplacement) {
   Replacements Replaces;
   // Test adding an insertion at the offset of an existing replacement.
   auto Err = Replaces.add(Replacement("x.cc", 10, 3, "replace"));
   EXPECT_TRUE(!Err);
   llvm::consumeError(std::move(Err));
   Err = Replaces.add(Replacement("x.cc", 10, 0, "insert"));
-  EXPECT_TRUE((bool)Err);
+  EXPECT_TRUE(!Err);
   llvm::consumeError(std::move(Err));
+  EXPECT_EQ(Replaces.size(), 2u);
 
   Replaces.clear();
   // Test overlap with an existing insertion.
@@ -131,8 +132,9 @@ TEST_F(ReplacementTest, FailAddOverlappingInsertions) {
   EXPECT_TRUE(!Err);
   llvm::consumeError(std::move(Err));
   Err = Replaces.add(Replacement("x.cc", 10, 3, "replace"));
-  EXPECT_TRUE((bool)Err);
+  EXPECT_TRUE(!Err);
   llvm::consumeError(std::move(Err));
+  EXPECT_EQ(Replaces.size(), 2u);
 }
 
 TEST_F(ReplacementTest, FailAddRegression) {
@@ -157,14 +159,24 @@ TEST_F(ReplacementTest, FailAddRegression) {
   llvm::consumeError(std::move(Err));
 }
 
-TEST_F(ReplacementTest, FailAddInsertAtOffsetOfReplacement) {
+TEST_F(ReplacementTest, InsertAtOffsetOfReplacement) {
   Replacements Replaces;
   auto Err = Replaces.add(Replacement("x.cc", 10, 2, ""));
   EXPECT_TRUE(!Err);
   llvm::consumeError(std::move(Err));
   Err = Replaces.add(Replacement("x.cc", 10, 0, ""));
-  EXPECT_TRUE((bool)Err);
+  EXPECT_TRUE(!Err);
+  llvm::consumeError(std::move(Err));
+  EXPECT_EQ(Replaces.size(), 2u);
+
+  Replaces.clear();
+  Err = Replaces.add(Replacement("x.cc", 10, 0, ""));
+  EXPECT_TRUE(!Err);
+  llvm::consumeError(std::move(Err));
+  Err = Replaces.add(Replacement("x.cc", 10, 2, ""));
+  EXPECT_TRUE(!Err);
   llvm::consumeError(std::move(Err));
+  EXPECT_EQ(Replaces.size(), 2u);
 }
 
 TEST_F(ReplacementTest, FailAddInsertAtOtherInsert) {
@@ -175,6 +187,38 @@ TEST_F(ReplacementTest, FailAddInsertAtOtherInsert) {
   Err = Replaces.add(Replacement("x.cc", 10, 0, "b"));
   EXPECT_TRUE((bool)Err);
   llvm::consumeError(std::move(Err));
+
+  Replaces.clear();
+  Err = Replaces.add(Replacement("x.cc", 10, 0, ""));
+  EXPECT_TRUE(!Err);
+  llvm::consumeError(std::move(Err));
+  Err = Replaces.add(Replacement("x.cc", 10, 0, ""));
+  EXPECT_TRUE((bool)Err);
+  llvm::consumeError(std::move(Err));
+
+  Replaces.clear();
+  Err = Replaces.add(Replacement("x.cc", 10, 0, ""));
+  EXPECT_TRUE(!Err);
+  llvm::consumeError(std::move(Err));
+  Err = Replaces.add(Replacement("x.cc", 10, 3, ""));
+  EXPECT_TRUE(!Err);
+  llvm::consumeError(std::move(Err));
+  Err = Replaces.add(Replacement("x.cc", 10, 0, ""));
+  EXPECT_TRUE((bool)Err);
+  llvm::consumeError(std::move(Err));
+}
+
+TEST_F(ReplacementTest, InsertBetweenAdjacentReplacements) {
+  Replacements Replaces;
+  auto Err = Replaces.add(Replacement("x.cc", 10, 5, "a"));
+  EXPECT_TRUE(!Err);
+  llvm::consumeError(std::move(Err));
+  Err = Replaces.add(Replacement("x.cc", 8, 2, "a"));
+  EXPECT_TRUE(!Err);
+  llvm::consumeError(std::move(Err));
+  Err = Replaces.add(Replacement("x.cc", 10, 0, "b"));
+  EXPECT_TRUE(!Err);
+  llvm::consumeError(std::move(Err));
 }
 
 TEST_F(ReplacementTest, CanApplyReplacements) {
@@ -189,6 +233,29 @@ TEST_F(ReplacementTest, CanApplyReplacements) {
   EXPECT_EQ("line1\nreplaced\nother\nline4", Context.getRewrittenText(ID));
 }
 
+// Verifies that replacement/deletion is applied before insertion at the same
+// offset.
+TEST_F(ReplacementTest, InsertAndDelete) {
+  FileID ID = Context.createInMemoryFile("input.cpp",
+                                         "line1\nline2\nline3\nline4");
+  Replacements Replaces = toReplacements(
+      {Replacement(Context.Sources, Context.getLocation(ID, 2, 1), 6, ""),
+       Replacement(Context.Sources, Context.getLocation(ID, 2, 1), 0,
+                   "other\n")});
+  EXPECT_TRUE(applyAllReplacements(Replaces, Context.Rewrite));
+  EXPECT_EQ("line1\nother\nline3\nline4", Context.getRewrittenText(ID));
+}
+
+TEST_F(ReplacementTest, AdjacentReplacements) {
+  FileID ID = Context.createInMemoryFile("input.cpp",
+                                         "ab");
+  Replacements Replaces = toReplacements(
+      {Replacement(Context.Sources, Context.getLocation(ID, 1, 1), 1, "x"),
+       Replacement(Context.Sources, Context.getLocation(ID, 1, 2), 1, "y")});
+  EXPECT_TRUE(applyAllReplacements(Replaces, Context.Rewrite));
+  EXPECT_EQ("xy", Context.getRewrittenText(ID));
+}
+
 TEST_F(ReplacementTest, SkipsDuplicateReplacements) {
   FileID ID = Context.createInMemoryFile("input.cpp",
                                          "line1\nline2\nline3\nline4");