Diagnostics: Add error code to the Diagnostic

Allows this to be formatted similarly to the severity.

Change-Id: I74cd863d8f1d94089ce753ab76a2c70784eb5553
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/33938
Commit-Queue: Ben Clayton <bclayton@google.com>
Reviewed-by: David Neto <dneto@google.com>

src/diagnostic/diagnostic.h

@@ -43,6 +43,9 @@ class Diagnostic {
   Source source;
   /// message is the text associated with the diagnostic.
   std::string message;
+  /// code is the error code, for example a validation error might have the code
+  /// `"v-0001"`.
+  const char* code = nullptr;
 };
 
 /// List is a container of Diagnostic messages.

src/diagnostic/formatter.cc

@@ -16,6 +16,7 @@
 
 #include <algorithm>
 #include <sstream>
+#include <vector>
 
 #include "src/diagnostic/diagnostic.h"
 #include "src/diagnostic/printer.h"
@@ -24,38 +25,29 @@ namespace tint {
 namespace diag {
 namespace {
 
-template <typename CharT, typename Traits>
-std::basic_ostream<CharT, Traits>& operator<<(
-    std::basic_ostream<CharT, Traits>& stream,
-    Severity severity) {
+const char* to_str(Severity severity) {
   switch (severity) {
     case Severity::Info:
-      stream << "info";
-      break;
+      return "info";
     case Severity::Warning:
-      stream << "warning";
-      break;
+      return "warning";
     case Severity::Error:
-      stream << "error";
-      break;
+      return "error";
     case Severity::Fatal:
-      stream << "fatal";
-      break;
+      return "fatal";
   }
-  return stream;
+  return "";
 }
 
-template <typename CharT, typename Traits>
-std::basic_ostream<CharT, Traits>& operator<<(
-    std::basic_ostream<CharT, Traits>& stream,
-    const Source::Location& location) {
+std::string to_str(const Source::Location& location) {
+  std::stringstream ss;
   if (location.line > 0) {
-    stream << location.line;
+    ss << location.line;
     if (location.column > 0) {
-      stream << ":" << location.column;
+      ss << ":" << location.column;
     }
   }
-  return stream;
+  return ss.str();
 }
 
 }  // namespace
@@ -134,40 +126,59 @@ void Formatter::format(const List& list, Printer* printer) const {
 void Formatter::format(const Diagnostic& diag, State& state) const {
   auto const& src = diag.source;
   auto const& rng = src.range;
+  bool has_code = diag.code != nullptr && diag.code[0] != '\0';
 
   state.set_style({Color::kDefault, true});
 
-  bool emit_colon = true;
+  struct TextAndColor {
+    std::string text;
+    Color color;
+    bool bold = false;
+  };
+  std::vector<TextAndColor> prefix;
+  prefix.reserve(6);
+
   if (style_.print_file && src.file != nullptr && !src.file->path.empty()) {
-    state << src.file->path;
     if (rng.begin.line > 0) {
-      state << ":" << rng.begin;
+      prefix.emplace_back(TextAndColor{src.file->path + ":" + to_str(rng.begin),
+                                       Color::kDefault});
+    } else {
+      prefix.emplace_back(TextAndColor{src.file->path, Color::kDefault});
     }
   } else if (rng.begin.line > 0) {
-    state << rng.begin;
-  } else {
-    // No position infomation was printed, so don't start the line with a colon.
-    emit_colon = false;
+    prefix.emplace_back(TextAndColor{to_str(rng.begin), Color::kDefault});
+  }
+
+  Color severity_color = Color::kDefault;
+  switch (diag.severity) {
+    case Severity::Warning:
+      severity_color = Color::kYellow;
+      break;
+    case Severity::Error:
+    case Severity::Fatal:
+      severity_color = Color::kRed;
+      break;
+    default:
+      break;
   }
   if (style_.print_severity) {
-    switch (diag.severity) {
-      case Severity::Warning:
-        state.set_style({Color::kYellow, true});
-        break;
-      case Severity::Error:
-      case Severity::Fatal:
-        state.set_style({Color::kRed, true});
-        break;
-      default:
-        break;
+    prefix.emplace_back(
+        TextAndColor{to_str(diag.severity), severity_color, true});
+  }
+  if (has_code) {
+    prefix.emplace_back(TextAndColor{diag.code, severity_color});
+  }
+
+  for (size_t i = 0; i < prefix.size(); i++) {
+    if (i > 0) {
+      state << " ";
     }
-    state << " " << diag.severity << ": ";
-    // A colon was just printed, don't repeat it.
-    emit_colon = false;
+    state.set_style({prefix[i].color, prefix[i].bold});
+    state << prefix[i].text;
   }
 
   state.set_style({Color::kDefault, true});
-  if (emit_colon) {
+  if (!prefix.empty()) {
     state << ": ";
   }
   state << diag.message;

src/diagnostic/formatter_test.cc

@@ -37,7 +37,8 @@ class DiagFormatterTest : public testing::Test {
   Diagnostic diag_warn{Severity::Warning,
                        Source{Source::Range{{2, 14}, {2, 18}}, &file}, "grrr"};
   Diagnostic diag_err{Severity::Error,
-                      Source{Source::Range{{3, 16}, {3, 21}}, &file}, "hiss"};
+                      Source{Source::Range{{3, 16}, {3, 21}}, &file}, "hiss",
+                      "abc123"};
   Diagnostic diag_fatal{Severity::Fatal,
                         Source{Source::Range{{4, 16}, {4, 19}}, &file},
                         "nothing"};
@@ -48,7 +49,7 @@ TEST_F(DiagFormatterTest, Simple) {
   auto got = fmt.format(List{diag_info, diag_warn, diag_err, diag_fatal});
   auto* expect = R"(1:14: purr
 2:14: grrr
-3:16: hiss
+3:16 abc123: hiss
 4:16: nothing)";
   ASSERT_EQ(expect, got);
 }
@@ -66,7 +67,7 @@ TEST_F(DiagFormatterTest, WithFile) {
   auto got = fmt.format(List{diag_info, diag_warn, diag_err, diag_fatal});
   auto* expect = R"(file.name:1:14: purr
 file.name:2:14: grrr
-file.name:3:16: hiss
+file.name:3:16 abc123: hiss
 file.name:4:16: nothing)";
   ASSERT_EQ(expect, got);
 }
@@ -76,7 +77,7 @@ TEST_F(DiagFormatterTest, WithSeverity) {
   auto got = fmt.format(List{diag_info, diag_warn, diag_err, diag_fatal});
   auto* expect = R"(1:14 info: purr
 2:14 warning: grrr
-3:16 error: hiss
+3:16 error abc123: hiss
 4:16 fatal: nothing)";
   ASSERT_EQ(expect, got);
 }
@@ -92,7 +93,7 @@ the cat says meow
 the dog says woof
              ^^^^
 
-3:16: hiss
+3:16 abc123: hiss
 the snake says quack
                ^^^^^
 
@@ -114,7 +115,7 @@ file.name:2:14 warning: grrr
 the dog says woof
              ^^^^
 
-file.name:3:16 error: hiss
+file.name:3:16 error abc123: hiss
 the snake says quack
                ^^^^^