[clang-tools-extra] [clang-tidy] Don't insert blank line in IncludeInserter (PR #221428)

[Baranov Victor via cfe-commits]

https://github.com/vbvictor updated https://github.com/llvm/llvm-project/pull/221428

>From 4ed652fe77dae0bd5bd644bb400105a44a1f1e1c Mon Sep 17 00:00:00 2001
From: Victor Baranov <bar.victor.2002 at gmail.com>
Date: Sat, 5 Sep 2026 12:53:06 +0300
Subject: [PATCH] [clang-tidy] Don't insert blank line in IncludeInserter

---
 clang-tools-extra/clang-tidy/utils/IncludeSorter.cpp     | 7 +++----
 clang-tools-extra/docs/ReleaseNotes.md                   | 4 ++++
 .../unittests/clang-tidy/IncludeInserterTest.cpp         | 9 ---------
 .../clang-tidy/TransformerClangTidyCheckTest.cpp         | 2 --
 4 files changed, 7 insertions(+), 15 deletions(-)

diff --git a/clang-tools-extra/clang-tidy/utils/IncludeSorter.cpp b/clang-tools-extra/clang-tidy/utils/IncludeSorter.cpp
index b7c313693781d..826c3d2676e88 100644
--- a/clang-tools-extra/clang-tidy/utils/IncludeSorter.cpp
+++ b/clang-tools-extra/clang-tidy/utils/IncludeSorter.cpp
@@ -199,19 +199,18 @@ IncludeSorter::createIncludeInsertion(StringRef FileName, bool IsAngled) {
     return std::nullopt;
 
   if (NonEmptyKind < IncludeKind) {
-    // Create a block after.
+    // Insert directly after the nearest preceding group.
+    // This keeps clang-format able to fix up the ordering within group.
     const std::string &LastInclude = IncludeBucket[NonEmptyKind].back();
     const SourceRange LastIncludeLocation =
         IncludeLocations[LastInclude].back();
-    IncludeStmt.insert(0, LineEnding);
     return FixItHint::CreateInsertion(LastIncludeLocation.getEnd(),
                                       IncludeStmt);
   }
-  // Create a block before.
+  // Insert directly before the nearest group for the same reason as above.
   const std::string &FirstInclude = IncludeBucket[NonEmptyKind][0];
   const SourceRange FirstIncludeLocation =
       IncludeLocations[FirstInclude].back();
-  IncludeStmt.append(LineEnding);
   return FixItHint::CreateInsertion(FirstIncludeLocation.getBegin(),
                                     IncludeStmt);
 }
diff --git a/clang-tools-extra/docs/ReleaseNotes.md b/clang-tools-extra/docs/ReleaseNotes.md
index b32b8a51e0606..c0ff5b0cc096b 100644
--- a/clang-tools-extra/docs/ReleaseNotes.md
+++ b/clang-tools-extra/docs/ReleaseNotes.md
@@ -261,6 +261,10 @@ infrastructure are described first, followed by tool-specific sections.
 
 #### Miscellaneous
 
+- Fixed clang-tidy adding an unwanted blank line when automatically inserting
+  a missing `#include`, which stopped `clang-format` and `llvm-include-order`
+  from being able to sort it correctly afterward.
+
 ### Improvements to include-fixer
 
 ### Improvements to clang-include-fixer
diff --git a/clang-tools-extra/unittests/clang-tidy/IncludeInserterTest.cpp b/clang-tools-extra/unittests/clang-tidy/IncludeInserterTest.cpp
index d01ba9814b8a1..b01bcc8e69d63 100644
--- a/clang-tools-extra/unittests/clang-tidy/IncludeInserterTest.cpp
+++ b/clang-tools-extra/unittests/clang-tidy/IncludeInserterTest.cpp
@@ -392,7 +392,6 @@ void foo() {
 
 #include <list>
 #include <map>
-
 #include "path/to/header.h"
 
 void foo() {
@@ -413,7 +412,6 @@ void foo() {
 })";
   const char *PostCode = R"(
 #include "clang_tidy/tests/insert_includes_test_header.h"
-
 #include "path/to/header.h"
 
 void foo() {
@@ -524,7 +522,6 @@ void foo() {
 })";
   const char *PostCode = R"(
 #include "clang_tidy/tests/insert_includes_test_header.h"
-
 #include <set>
 
 #include "path/to/a/header.h"
@@ -553,7 +550,6 @@ void foo() {
 #include "clang_tidy/tests/insert_includes_test_header.h"
 
 #include <stdlib.h>
-
 #include <set>
 
 #include "path/to/a/header.h"
@@ -576,7 +572,6 @@ void foo() {
 })";
   const char *PostCode = R"(
 #include <set>
-
 #include "path/to/a/header.h"
 
 void foo() {
@@ -600,7 +595,6 @@ void foo() {
 })";
   const char *PostCode = R"(
 #include <stdlib.h>
-
 #include <set>
 
 #include "path/to/a/header.h"
@@ -718,7 +712,6 @@ void foo() {
 })";
   const char *PostCode = R"(
 #include "clang_tidy/tests/insert_includes_test_header.h"
-
 #include <c.h>
 
 #include <d>
@@ -747,7 +740,6 @@ void foo() {
 })";
   const char *PostCode = R"(
 #import "clang_tidy/tests/insert_includes_test_header.h"
-
 #import "a/header.h"
 
 void foo() {
@@ -798,7 +790,6 @@ void foo() {
 #include <map>
 
 #include "path/to/a/header.h"
-
 #import "clang_tidy/tests/generated_file.proto.h"
 
 void foo() {
diff --git a/clang-tools-extra/unittests/clang-tidy/TransformerClangTidyCheckTest.cpp b/clang-tools-extra/unittests/clang-tidy/TransformerClangTidyCheckTest.cpp
index fc43f2579e8e2..612229a4f1eb1 100644
--- a/clang-tools-extra/unittests/clang-tidy/TransformerClangTidyCheckTest.cpp
+++ b/clang-tools-extra/unittests/clang-tidy/TransformerClangTidyCheckTest.cpp
@@ -335,7 +335,6 @@ TEST(TransformerClangTidyCheckTest, AddIncludeObeysSortStyleLocalOption) {
 int h(int x) { return 3; })cc";
 
   std::string TreatsAsLibraryHeader = R"cc(#include "input.h"
-
 #include "bar.h"
 int h(int x) { return 5; })cc";
 
@@ -367,7 +366,6 @@ TEST(TransformerClangTidyCheckTest, AddIncludeObeysSortStyleGlobalOption) {
 int h(int x) { return 3; })cc";
 
   std::string TreatsAsLibraryHeader = R"cc(#include "input.h"
-
 #include "bar.h"
 int h(int x) { return 5; })cc";