From 14ea15614778ef140a5bd83e725412c0ee4b8800 Mon Sep 17 00:00:00 2001
From: Martin Probst <martin@probst.io>
Date: Wed, 8 Jun 2016 14:04:04 +0000
Subject: [PATCH] clang-format: [JS] fix an assertion failure caused by
 shrinking sources.

Summary:
The JavaScript import sorter has a corner condition that can cause the overall
source text length to shrink. This change circumvents the issue by appending
trailing space in the line after the import blocks to match at least the
previous source code length.

This needs a better long term fix, but this fixes the immediate issue.

Reviewers: alexeagle, djasper

Subscribers: klimek

Differential Revision: http://reviews.llvm.org/D21108

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@272142 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Format/SortJavaScriptImports.cpp   | 17 +++++++++++++++--
 unittests/Format/SortImportsTestJS.cpp | 13 +++++++++++++
 2 files changed, 28 insertions(+), 2 deletions(-)

diff --git a/lib/Format/SortJavaScriptImports.cpp b/lib/Format/SortJavaScriptImports.cpp
index 28c3ae9f6a..fc2a653492 100644
--- a/lib/Format/SortJavaScriptImports.cpp
+++ b/lib/Format/SortJavaScriptImports.cpp
@@ -170,12 +170,25 @@ public:
     if (ReferencesInOrder && SymbolsInOrder)
       return Result;
 
+    SourceRange InsertionPoint = References[0].Range;
+    InsertionPoint.setEnd(References[References.size() - 1].Range.getEnd());
+
+    // The loop above might collapse previously existing line breaks between
+    // import blocks, and thus shrink the file. SortIncludes must not shrink
+    // overall source length as there is currently no re-calculation of ranges
+    // after applying source sorting.
+    // This loop just backfills trailing spaces after the imports, which are
+    // harmless and will be stripped by the subsequent formatting pass.
+    // TODO: A better long term fix is to re-calculate Ranges after sorting.
+    unsigned PreviousSize = getSourceText(InsertionPoint).size();
+    while (ReferencesText.size() < PreviousSize) {
+      ReferencesText += " ";
+    }
+
     // Separate references from the main code body of the file.
     if (FirstNonImportLine && FirstNonImportLine->First->NewlinesBefore < 2)
       ReferencesText += "\n";
 
-    SourceRange InsertionPoint = References[0].Range;
-    InsertionPoint.setEnd(References[References.size() - 1].Range.getEnd());
     DEBUG(llvm::dbgs() << "Replacing imports:\n"
                        << getSourceText(InsertionPoint) << "\nwith:\n"
                        << ReferencesText << "\n");
diff --git a/unittests/Format/SortImportsTestJS.cpp b/unittests/Format/SortImportsTestJS.cpp
index 140fe4a746..17e73b0855 100644
--- a/unittests/Format/SortImportsTestJS.cpp
+++ b/unittests/Format/SortImportsTestJS.cpp
@@ -223,6 +223,19 @@ TEST_F(SortImportsTestJS, AffectedRange) {
              24, 30);
 }
 
+TEST_F(SortImportsTestJS, SortingCanShrink) {
+  // Sort excluding a suffix.
+  verifySort("import {B} from 'a';\n"
+             "import {A} from 'b';\n"
+             "\n"
+             "1;",
+             "import {A} from 'b';\n"
+             "\n"
+             "import {B} from 'a';\n"
+             "\n"
+             "1;");
+}
+
 } // end namespace
 } // end namespace format
 } // end namespace clang
-- 
2.50.1