[clang] [clang][Diagnostics] Highlight code snippets (PR #66514)

Timm Baeder via cfe-commits cfe-commits at lists.llvm.org
Fri Sep 15 07:01:59 PDT 2023


https://github.com/tbaederr created https://github.com/llvm/llvm-project/pull/66514

Add some primitive syntax highlighting to our code snippet output.


Before:
![Screenshot from 2023-09-15 16-00-23](https://github.com/llvm/llvm-project/assets/49720664/8e43767a-d939-4c9f-ac2d-65e2df5de1f2)


After:
![Screenshot from 2023-09-15 15-55-35](https://github.com/llvm/llvm-project/assets/49720664/714b536c-377f-4a0d-921c-b103b90c5706)






_Obviously_ this is kinda WIP and more of a hack in general, but IMO it increases readability of the source snippets (which people look at highlighted all the time anyway...) and LLDB does something similar, so let's see.


>From b4f4d29c8780752629f78b4debb86bd9f9dff0d3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timm=20B=C3=A4der?= <tbaeder at redhat.com>
Date: Fri, 15 Sep 2023 15:51:39 +0200
Subject: [PATCH] [clang][Diagnostics] Highlight code snippets

Add some primitive syntax highlighting to our code snippet output.
---
 .../clang/Frontend/CodeSnippetHighlighter.h   |  46 +++++++
 clang/include/clang/Frontend/TextDiagnostic.h |   4 +-
 clang/lib/Frontend/CMakeLists.txt             |   1 +
 clang/lib/Frontend/CodeSnippetHighlighter.cpp | 120 ++++++++++++++++++
 clang/lib/Frontend/TextDiagnostic.cpp         |  31 ++++-
 5 files changed, 199 insertions(+), 3 deletions(-)
 create mode 100644 clang/include/clang/Frontend/CodeSnippetHighlighter.h
 create mode 100644 clang/lib/Frontend/CodeSnippetHighlighter.cpp

diff --git a/clang/include/clang/Frontend/CodeSnippetHighlighter.h b/clang/include/clang/Frontend/CodeSnippetHighlighter.h
new file mode 100644
index 000000000000000..776954b59e2e1a8
--- /dev/null
+++ b/clang/include/clang/Frontend/CodeSnippetHighlighter.h
@@ -0,0 +1,46 @@
+//===--- CodeSnippetHighlighter.h - Code snippet highlighting ---*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_FRONTEND_CODESNIPPETHIGHLIGHTER_H
+#define LLVM_CLANG_FRONTEND_CODESNIPPETHIGHLIGHTER_H
+
+#include "clang/Basic/LangOptions.h"
+#include "llvm/ADT/SmallSet.h"
+#include "llvm/Support/raw_ostream.h"
+#include <vector>
+
+namespace clang {
+
+struct StyleRange {
+  unsigned Start;
+  unsigned End;
+  const enum llvm::raw_ostream::Colors c;
+};
+
+class CodeSnippetHighlighter final {
+public:
+  CodeSnippetHighlighter() = default;
+
+  /// Produce StyleRanges for the given line.
+  /// The returned vector contains non-overlapping style ranges. They are sorted
+  /// from beginning of the line to the end.
+  std::vector<StyleRange> highlightLine(llvm::StringRef SourceLine,
+                                        const LangOptions &LangOpts);
+
+private:
+  bool Initialized = false;
+  /// Fills Keywords and Literals.
+  void ensureTokenData();
+
+  llvm::SmallSet<StringRef, 12> Keywords;
+  llvm::SmallSet<StringRef, 12> Literals;
+};
+
+} // namespace clang
+
+#endif
diff --git a/clang/include/clang/Frontend/TextDiagnostic.h b/clang/include/clang/Frontend/TextDiagnostic.h
index 7eb0ab0cdc9bca8..39e09fe553dd4b9 100644
--- a/clang/include/clang/Frontend/TextDiagnostic.h
+++ b/clang/include/clang/Frontend/TextDiagnostic.h
@@ -15,6 +15,7 @@
 #ifndef LLVM_CLANG_FRONTEND_TEXTDIAGNOSTIC_H
 #define LLVM_CLANG_FRONTEND_TEXTDIAGNOSTIC_H
 
+#include "clang/Frontend/CodeSnippetHighlighter.h"
 #include "clang/Frontend/DiagnosticRenderer.h"
 
 namespace clang {
@@ -33,6 +34,7 @@ namespace clang {
 /// printing coming out of libclang.
 class TextDiagnostic : public DiagnosticRenderer {
   raw_ostream &OS;
+  CodeSnippetHighlighter SnippetHighlighter;
 
 public:
   TextDiagnostic(raw_ostream &OS,
@@ -104,7 +106,7 @@ class TextDiagnostic : public DiagnosticRenderer {
                            ArrayRef<FixItHint> Hints);
 
   void emitSnippet(StringRef SourceLine, unsigned MaxLineNoDisplayWidth,
-                   unsigned LineNo);
+                   unsigned LineNo, bool A, const SourceManager &SM);
 
   void emitParseableFixits(ArrayRef<FixItHint> Hints, const SourceManager &SM);
 };
diff --git a/clang/lib/Frontend/CMakeLists.txt b/clang/lib/Frontend/CMakeLists.txt
index 1e5f0a859dfd568..f3547f771593093 100644
--- a/clang/lib/Frontend/CMakeLists.txt
+++ b/clang/lib/Frontend/CMakeLists.txt
@@ -42,6 +42,7 @@ add_clang_library(clangFrontend
   TextDiagnosticPrinter.cpp
   VerifyDiagnosticConsumer.cpp
   InterfaceStubFunctionsConsumer.cpp
+  CodeSnippetHighlighter.cpp
 
   DEPENDS
   ClangDriverOptions
diff --git a/clang/lib/Frontend/CodeSnippetHighlighter.cpp b/clang/lib/Frontend/CodeSnippetHighlighter.cpp
new file mode 100644
index 000000000000000..829a533ad2692e5
--- /dev/null
+++ b/clang/lib/Frontend/CodeSnippetHighlighter.cpp
@@ -0,0 +1,120 @@
+
+#include "clang/Frontend/CodeSnippetHighlighter.h"
+#include "clang/Basic/DiagnosticOptions.h"
+#include "clang/Basic/SourceManager.h"
+#include "clang/Lex/Lexer.h"
+#include "llvm/Support/raw_ostream.h"
+
+using namespace clang;
+
+void CodeSnippetHighlighter::ensureTokenData() {
+  if (Initialized)
+    return;
+
+  // List of keywords, literals and types we want to highlight.
+  // These are best-effort, as is everything we do wrt. highlighting.
+  Keywords.insert("_Static_assert");
+  Keywords.insert("auto");
+  Keywords.insert("concept");
+  Keywords.insert("const");
+  Keywords.insert("consteval");
+  Keywords.insert("constexpr");
+  Keywords.insert("delete");
+  Keywords.insert("do");
+  Keywords.insert("else");
+  Keywords.insert("final");
+  Keywords.insert("for");
+  Keywords.insert("if");
+  Keywords.insert("mutable");
+  Keywords.insert("namespace");
+  Keywords.insert("new");
+  Keywords.insert("private");
+  Keywords.insert("public");
+  Keywords.insert("requires");
+  Keywords.insert("return");
+  Keywords.insert("static");
+  Keywords.insert("static_assert");
+  Keywords.insert("using");
+  Keywords.insert("void");
+  Keywords.insert("volatile");
+  Keywords.insert("while");
+
+  // Builtin types we highlight
+  Keywords.insert("void");
+  Keywords.insert("char");
+  Keywords.insert("short");
+  Keywords.insert("int");
+  Keywords.insert("unsigned");
+  Keywords.insert("long");
+  Keywords.insert("float");
+  Keywords.insert("double");
+
+  Literals.insert("true");
+  Literals.insert("false");
+  Literals.insert("nullptr");
+
+  Initialized = true;
+}
+
+static SourceManager createTempSourceManager() {
+  FileSystemOptions FileOpts;
+  FileManager FileMgr(FileOpts);
+  llvm::IntrusiveRefCntPtr<DiagnosticIDs> DiagIDs(new DiagnosticIDs());
+  llvm::IntrusiveRefCntPtr<DiagnosticOptions> DiagOpts(new DiagnosticOptions());
+  DiagnosticsEngine diags(DiagIDs, DiagOpts);
+  return SourceManager(diags, FileMgr);
+}
+
+static Lexer createTempLexer(llvm::MemoryBufferRef B, SourceManager &FakeSM,
+                             const LangOptions &LangOpts) {
+  return Lexer(FakeSM.createFileID(B), B, FakeSM, LangOpts);
+}
+
+std::vector<StyleRange>
+CodeSnippetHighlighter::highlightLine(StringRef SourceLine,
+                                      const LangOptions &LangOpts) {
+  ensureTokenData();
+
+  constexpr raw_ostream::Colors CommentColor = raw_ostream::BLACK;
+  constexpr raw_ostream::Colors LiteralColor = raw_ostream::GREEN;
+  constexpr raw_ostream::Colors KeywordColor = raw_ostream::YELLOW;
+
+  const auto MemBuf = llvm::MemoryBuffer::getMemBuffer(SourceLine);
+  SourceManager FakeSM = createTempSourceManager();
+  Lexer L = createTempLexer(MemBuf->getMemBufferRef(), FakeSM, LangOpts);
+  L.SetKeepWhitespaceMode(true);
+
+  std::vector<StyleRange> Styles;
+  bool Stop = false;
+  while (!Stop) {
+    Token tok;
+    Stop = L.LexFromRawLexer(tok);
+    if (tok.is(tok::unknown))
+      continue;
+
+    bool Invalid;
+    unsigned Start =
+        FakeSM.getSpellingColumnNumber(tok.getLocation(), &Invalid) - 1;
+    if (Invalid)
+      continue;
+
+    if (tok.is(tok::raw_identifier)) {
+      // Almost everything we lex is an identifier, since we use a raw lexer.
+      // Some should be highlightes as literals, others as keywords.
+      if (Keywords.contains(tok.getRawIdentifier()))
+        Styles.push_back(
+            StyleRange{Start, Start + tok.getLength(), KeywordColor});
+      else if (Literals.contains(tok.getRawIdentifier()))
+        Styles.push_back(
+            StyleRange{Start, Start + tok.getLength(), LiteralColor});
+    } else if (tok::isLiteral(tok.getKind())) {
+      Styles.push_back(
+          StyleRange{Start, Start + tok.getLength(), LiteralColor});
+    } else if (tok.is(tok::comment)) {
+      Styles.push_back(
+          StyleRange{Start, Start + tok.getLength(), CommentColor});
+    }
+  }
+
+  return Styles;
+}
diff --git a/clang/lib/Frontend/TextDiagnostic.cpp b/clang/lib/Frontend/TextDiagnostic.cpp
index eaa6e8d29a1dece..a7a2405d9bbae6d 100644
--- a/clang/lib/Frontend/TextDiagnostic.cpp
+++ b/clang/lib/Frontend/TextDiagnostic.cpp
@@ -11,6 +11,7 @@
 #include "clang/Basic/DiagnosticOptions.h"
 #include "clang/Basic/FileManager.h"
 #include "clang/Basic/SourceManager.h"
+#include "clang/Frontend/CodeSnippetHighlighter.h"
 #include "clang/Lex/Lexer.h"
 #include "llvm/ADT/SmallString.h"
 #include "llvm/ADT/StringExtras.h"
@@ -1248,7 +1249,7 @@ void TextDiagnostic::emitSnippetAndCaret(
     }
 
     // Emit what we have computed.
-    emitSnippet(SourceLine, MaxLineNoDisplayWidth, DisplayLineNo);
+    emitSnippet(SourceLine, MaxLineNoDisplayWidth, DisplayLineNo, false, SM);
 
     if (!CaretLine.empty()) {
       indentForLineNumbers();
@@ -1278,7 +1279,11 @@ void TextDiagnostic::emitSnippetAndCaret(
 
 void TextDiagnostic::emitSnippet(StringRef SourceLine,
                                  unsigned MaxLineNoDisplayWidth,
-                                 unsigned LineNo) {
+                                 unsigned LineNo, bool IsSlash,
+                                 const SourceManager &SM) {
+  std::vector<StyleRange> Styles =
+      SnippetHighlighter.highlightLine(SourceLine, LangOpts);
+
   // Emit line number.
   if (MaxLineNoDisplayWidth > 0) {
     unsigned LineNoDisplayWidth = getNumDisplayWidth(LineNo);
@@ -1288,11 +1293,33 @@ void TextDiagnostic::emitSnippet(StringRef SourceLine,
 
   // Print the source line one character at a time.
   bool PrintReversed = false;
+  bool HighlightingEnabled = DiagOpts->ShowColors;
   size_t I = 0;
   while (I < SourceLine.size()) {
     auto [Str, WasPrintable] =
         printableTextForNextCharacter(SourceLine, &I, DiagOpts->TabStop);
 
+    // Just stop highlighting anything for this line if we found a non-printable
+    // character.
+    if (!WasPrintable)
+      HighlightingEnabled = false;
+
+    // FIXME: I hope we can do this in some nicer way.
+    if (HighlightingEnabled) {
+      std::optional<enum raw_ostream::Colors> H;
+      for (auto &P : Styles) {
+        if (P.Start < I && P.End >= I) {
+          H = P.c;
+          break;
+        }
+      }
+
+      if (H) {
+        OS.changeColor(*H, false);
+      } else
+        OS.resetColor();
+    }
+
     // Toggle inverted colors on or off for this character.
     if (DiagOpts->ShowColors) {
       if (WasPrintable == PrintReversed) {



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