[clang] [clang-format] Reuse AlignTokens for aligning macros (PR #164120)

[Björn Schäpers via cfe-commits]

https://github.com/HazardyKnusperkeks created https://github.com/llvm/llvm-project/pull/164120

Fixes #52985.

This leaves aligning short case statements with its own logic. But that is harder to port, because it aligns even with no content of the right hand side of the :.

>From 799514ea17019c2c05d25cbcb0f3ec07624b4c01 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Bj=C3=B6rn=20Sch=C3=A4pers?= <bjoern at hazardy.de>
Date: Sat, 18 Oct 2025 21:58:35 +0200
Subject: [PATCH] [clang-format] Reuse AlignTokens for aligning macros

Fixes #52985.

This leaves aligning short case statements with its own logic. But that
is harder to port, because it aligns even with no content of the right
hand side of the :.
---
 clang/lib/Format/WhitespaceManager.cpp | 88 ++++++--------------------
 clang/unittests/Format/FormatTest.cpp  |  5 ++
 2 files changed, 26 insertions(+), 67 deletions(-)

diff --git a/clang/lib/Format/WhitespaceManager.cpp b/clang/lib/Format/WhitespaceManager.cpp
index 7348a3af8cf95..19984fdfa98fd 100644
--- a/clang/lib/Format/WhitespaceManager.cpp
+++ b/clang/lib/Format/WhitespaceManager.cpp
@@ -432,7 +432,11 @@ AlignTokenSequence(const FormatStyle &Style, unsigned Start, unsigned End,
 // right-justified. It is used to align compound assignments like `+=` and `=`.
 // When RightJustify and ACS.PadOperators are true, operators in each block to
 // be aligned will be padded on the left to the same length before aligning.
-template <typename F>
+//
+// The simple check will not look at the indentaion and nesting level to recurse
+// into the line for alignment. It will also not count the commas. This is e.g.
+// for aligning macro definitions.
+template <typename F, bool SimpleCheck = false>
 static unsigned AlignTokens(const FormatStyle &Style, F &&Matches,
                             SmallVector<WhitespaceManager::Change, 16> &Changes,
                             unsigned StartAt,
@@ -465,9 +469,9 @@ static unsigned AlignTokens(const FormatStyle &Style, F &&Matches,
 
   // Measure the scope level (i.e. depth of (), [], {}) of the first token, and
   // abort when we hit any token in a higher scope than the starting one.
-  auto IndentAndNestingLevel = StartAt < Changes.size()
-                                   ? Changes[StartAt].indentAndNestingLevel()
-                                   : std::tuple<unsigned, unsigned, unsigned>();
+  const auto IndentAndNestingLevel =
+      StartAt < Changes.size() ? Changes[StartAt].indentAndNestingLevel()
+                               : std::tuple<unsigned, unsigned, unsigned>();
 
   // Keep track of the number of commas before the matching tokens, we will only
   // align a sequence of matching tokens if they are preceded by the same number
@@ -536,14 +540,17 @@ static unsigned AlignTokens(const FormatStyle &Style, F &&Matches,
     if (CurrentChange.Tok->isNot(tok::comment))
       LineIsComment = false;
 
-    if (CurrentChange.Tok->is(tok::comma)) {
-      ++CommasBeforeMatch;
-    } else if (CurrentChange.indentAndNestingLevel() > IndentAndNestingLevel) {
-      // Call AlignTokens recursively, skipping over this scope block.
-      unsigned StoppedAt =
-          AlignTokens(Style, Matches, Changes, i, ACS, RightJustify);
-      i = StoppedAt - 1;
-      continue;
+    if (!SimpleCheck) {
+      if (CurrentChange.Tok->is(tok::comma)) {
+        ++CommasBeforeMatch;
+      } else if (CurrentChange.indentAndNestingLevel() >
+                 IndentAndNestingLevel) {
+        // Call AlignTokens recursively, skipping over this scope block.
+        unsigned StoppedAt =
+            AlignTokens(Style, Matches, Changes, i, ACS, RightJustify);
+        i = StoppedAt - 1;
+        continue;
+      }
     }
 
     if (!Matches(CurrentChange))
@@ -683,61 +690,8 @@ void WhitespaceManager::alignConsecutiveMacros() {
     return Current->Next->SpacesRequiredBefore == SpacesRequiredBefore;
   };
 
-  unsigned MinColumn = 0;
-
-  // Start and end of the token sequence we're processing.
-  unsigned StartOfSequence = 0;
-  unsigned EndOfSequence = 0;
-
-  // Whether a matching token has been found on the current line.
-  bool FoundMatchOnLine = false;
-
-  // Whether the current line consists only of comments
-  bool LineIsComment = true;
-
-  unsigned I = 0;
-  for (unsigned E = Changes.size(); I != E; ++I) {
-    if (Changes[I].NewlinesBefore != 0) {
-      EndOfSequence = I;
-
-      // Whether to break the alignment sequence because of an empty line.
-      bool EmptyLineBreak = (Changes[I].NewlinesBefore > 1) &&
-                            !Style.AlignConsecutiveMacros.AcrossEmptyLines;
-
-      // Whether to break the alignment sequence because of a line without a
-      // match.
-      bool NoMatchBreak =
-          !FoundMatchOnLine &&
-          !(LineIsComment && Style.AlignConsecutiveMacros.AcrossComments);
-
-      if (EmptyLineBreak || NoMatchBreak) {
-        AlignMatchingTokenSequence(StartOfSequence, EndOfSequence, MinColumn,
-                                   AlignMacrosMatches, Changes);
-      }
-
-      // A new line starts, re-initialize line status tracking bools.
-      FoundMatchOnLine = false;
-      LineIsComment = true;
-    }
-
-    if (Changes[I].Tok->isNot(tok::comment))
-      LineIsComment = false;
-
-    if (!AlignMacrosMatches(Changes[I]))
-      continue;
-
-    FoundMatchOnLine = true;
-
-    if (StartOfSequence == 0)
-      StartOfSequence = I;
-
-    unsigned ChangeMinColumn = Changes[I].StartOfTokenColumn;
-    MinColumn = std::max(MinColumn, ChangeMinColumn);
-  }
-
-  EndOfSequence = I;
-  AlignMatchingTokenSequence(StartOfSequence, EndOfSequence, MinColumn,
-                             AlignMacrosMatches, Changes);
+  AlignTokens<decltype(AlignMacrosMatches)&, /*DontRecurse=*/true>(
+      Style, AlignMacrosMatches, Changes, 0, Style.AlignConsecutiveMacros);
 }
 
 void WhitespaceManager::alignConsecutiveAssignments() {
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
index b9ad930164944..3564a8ede0a01 100644
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -18559,6 +18559,11 @@ TEST_F(FormatTest, AlignConsecutiveMacros) {
                "#define bbbb 4\n"
                "#define ccc       (5)",
                Style);
+
+  Style.ColumnLimit = 30;
+  verifyFormat("#define MY_FUNC(x) callMe(X)\n"
+               "#define MY_LONG_CONSTANT 17",
+               Style);
 }
 
 TEST_F(FormatTest, AlignConsecutiveAssignmentsAcrossEmptyLines) {