[clangd] strictly respect formatting range

[qchateau]

Summary

Clang format will often format a range of code wider then the requested format range. Returning a replacement outside of the requested range can mess with clients. Keeping the formatting in range of what the client asks gives more expected results and will limit the impact of partial formatting in diffs.

A specific example: a problem often occurs when using VSCode in "format modified lines" mode. The client will ask clangd to format two non-continugous lines, separately. Clangd replies to both requests with replacements for both lines, effectively providing four replacements in total. VSCode will either apply replacements twice (messing up the results) or simply error out and skip the formatting.

[qchateau]

fix tests

clang-tools-extra/clangd/ClangdServer.cpp

 //===--- ClangdServer.cpp - Main clangd server code --------------*- C++-*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===-------------------------------------------------------------------===//
 
auto Action = [File = File.str(), Code = std::move(*Code),
                  CB = std::move(CB), this]() mutable {
     format::FormatStyle Style = getFormatStyleForFile(File, Code, TFS);
     tooling::Replacements IncludeReplaces =
         format::sortIncludes(Style, Code, Ranges, File);
     auto Changed = tooling::applyAllReplacements(Code, IncludeReplaces);
     if (!Changed)
       return CB(Changed.takeError());
 
-    CB(IncludeReplaces.merge(format::reformat(
+    auto Replacements = IncludeReplaces.merge(format::reformat(
         Style, *Changed,
         tooling::calculateRangesAfterReplacements(IncludeReplaces, Ranges),
-        File)));
+        File));
+    clang::tooling::Replacements ReplacementsInRange;
+    for (const auto &Repl : Replacements) {
+      tooling::Range ReplRange{
+          Repl.getOffset(),
+          std::max<unsigned int>(Repl.getLength(),
+                                 Repl.getReplacementText().size()),
+      };
+      if (ReplRange.overlapsWith(Ranges.front())) {
+        if (auto Err = ReplacementsInRange.add(Repl)) {
+          CB(std::move(Err));
+        }
+      }
+    }
+    CB(ReplacementsInRange);
   };
   WorkScheduler->runQuick("Format", File, std::move(Action));
 }
 
 void ClangdServer::formatOnType(PathRef File, Position Pos,
                                 StringRef TriggerText,
                                 Callback<std::vector<TextEdit>> CB) {
   auto Code = getDraft(File);

clang-tools-extra/clangd/test/formatting.test

 # RUN: clangd -lit-test < %s | FileCheck -strict-whitespace %s
 {"jsonrpc":"2.0","id":0,"method":"initialize","params":{"processId":123,"rootPath":"clangd","capabilities":{},"trace":"off"}}
 ---
 {"jsonrpc":"2.0","method":"textDocument/didOpen","params":{"textDocument":{"uri":"test:///foo.c","languageId":"c","version":1,"text":"int foo ( int x ) {\n    x = x+1;\n    return x;\n    }"}}}
 ---
 {"jsonrpc":"2.0","id":1,"method":"textDocument/rangeFormatting","params":{"textDocument":{"uri":"test:///foo.c"},"range":{"start":{"line":1,"character":4},"end":{"line":1,"character":12}}}}
 #      CHECK:   "id": 1,
 # CHECK-NEXT:  "jsonrpc": "2.0",
 # CHECK-NEXT:  "result": [
 # CHECK-NEXT:    {
-# CHECK-NEXT:      "newText": "\n  ",
-# CHECK-NEXT:      "range": {
-# CHECK-NEXT:        "end": {
-# CHECK-NEXT:          "character": 4,
-# CHECK-NEXT:          "line": 1
-# CHECK-NEXT:        },
-# CHECK-NEXT:        "start": {
-# CHECK-NEXT:          "character": 19,
-# CHECK-NEXT:          "line": 0
-# CHECK-NEXT:        }
-# CHECK-NEXT:      }
-# CHECK-NEXT:    },
-# CHECK-NEXT:    {
 # CHECK-NEXT:      "newText": " ",
 # CHECK-NEXT:      "range": {
 # CHECK-NEXT:        "end": {
 # CHECK-NEXT:          "character": 9,
 # CHECK-NEXT:          "line": 1
 # CHECK-NEXT:        },
 # CHECK-NEXT:        "start": {
 # CHECK-NEXT:          "character": 9,
 # CHECK-NEXT:          "line": 1
 # CHECK-NEXT:        }
 # CHECK-NEXT:      }
 # CHECK-NEXT:    },
 # CHECK-NEXT:    {
 # CHECK-NEXT:      "newText": " ",
 # CHECK-NEXT:      "range": {
 # CHECK-NEXT:        "end": {
 # CHECK-NEXT:          "character": 10,
 # CHECK-NEXT:          "line": 1
 # CHECK-NEXT:        },
 # CHECK-NEXT:        "start": {
 # CHECK-NEXT:          "character": 10,
 # CHECK-NEXT:          "line": 1
 # CHECK-NEXT:        }
 # CHECK-NEXT:      }
-# CHECK-NEXT:    },
-# CHECK-NEXT:    {
-# CHECK-NEXT:      "newText": "\n  ",
-# CHECK-NEXT:      "range": {
-# CHECK-NEXT:        "end": {
-# CHECK-NEXT:          "character": 4,
-# CHECK-NEXT:          "line": 2
-# CHECK-NEXT:        },
-# CHECK-NEXT:        "start": {
-# CHECK-NEXT:          "character": 12,
-# CHECK-NEXT:          "line": 1
-# CHECK-NEXT:        }
-# CHECK-NEXT:      }
 # CHECK-NEXT:    }
 # CHECK-NEXT:  ]
 ---
 {"jsonrpc":"2.0","method":"textDocument/didChange","params":{"textDocument":{"uri":"test:///foo.c","version":5},"contentChanges":[{"text":"int foo ( int x ) {\n  x = x + 1;\n  return x;\n    }"}]}}
 #
 #
 ---
 {"jsonrpc":"2.0","id":2,"method":"textDocument/rangeFormatting","params":{"textDocument":{"uri":"test:///foo.c"},"range":{"start":{"line":1,"character":2},"end":{"line":1,"character":12}}}}