Extended error reporting for SVG attribute parsing

third_party/WebKit/Source/core/svg/SVGParsingError.cpp

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "core/svg/SVGParsingError.h"
+
+#include "core/dom/QualifiedName.h"
+#include "platform/JSONValues.h"
+#include "wtf/text/CharacterNames.h"
+#include "wtf/text/StringBuilder.h"
+
+#include <utility>
+
+namespace blink {
+
+namespace {
+
+void appendErrorContextInfo(StringBuilder& builder, const String& tagName, const QualifiedName& name)
+{
+    builder.append('<');
+    builder.append(tagName);
+    builder.appendLiteral("> attribute ");
+    builder.append(name.toString());
+}
+
+std::pair<const char*, const char*> messageForStatus(SVGParseStatus status)
+{
+    switch (status) {
+    case SVGParseStatus::TrailingGarbage:
+        return std::make_pair("Trailing garbage, ", ".");
+    case SVGParseStatus::ExpectedBoolean:
+        return std::make_pair("Expected 'true' or 'false', ", ".");
+    case SVGParseStatus::ExpectedEnumeration:
+        return std::make_pair("Unrecognized enumerated value, ", ".");
+    case SVGParseStatus::NegativeValue:
+        return std::make_pair("A negative value is not valid. (", ")");
+    case SVGParseStatus::ParsingFailed:
+    default:
+        ASSERT_NOT_REACHED();
+        break;
+    }
+    return std::make_pair("", "");
+}
+
+bool disableLocus(SVGParseStatus status)
+{
+    // Disable locus for semantic errors and generic errors (see TODO below).
+    return status == SVGParseStatus::NegativeValue
+        || status == SVGParseStatus::ParsingFailed;
+}
+
+void appendValue(StringBuilder& builder, SVGParsingError error, const AtomicString& value)
+{
+    builder.append('"');
+    if (!error.hasLocus() || disableLocus(error.status())) {
+        escapeStringForJSON(value.string(), &builder);
+    } else {
+        // Emit a string on the form: '"[...]<before><after>[...]"'
+        unsigned locus = error.locus();
+        ASSERT(locus <= value.length());
+
+        // Amount of context to show before/after the error.
+        const unsigned kContext = 16;
+
+        unsigned contextStart = std::max(locus, kContext) - kContext;
+        unsigned contextEnd = std::min(locus + kContext, value.length());
+        ASSERT(contextStart <= contextEnd);
+        ASSERT(contextEnd <= value.length());
+        if (contextStart != 0)
+            builder.append(horizontalEllipsisCharacter);
+        escapeStringForJSON(value.string().substring(contextStart, contextEnd - contextStart), &builder);
+        if (contextEnd != value.length())
+            builder.append(horizontalEllipsisCharacter);
+    }
+    builder.append('"');
+}
+
+}
+
+String SVGParsingError::format(const String& tagName, const QualifiedName& name, const AtomicString& value) const
+{
+    StringBuilder builder;
+
+    // TODO(fs): Remove this case once enough specific errors have been added.
+    if (status() == SVGParseStatus::ParsingFailed) {
+        builder.appendLiteral("Invalid value for ");
+        appendErrorContextInfo(builder, tagName, name);
+        builder.append('=');
+        appendValue(builder, *this, value);
+    } else {
+        appendErrorContextInfo(builder, tagName, name);
+        builder.appendLiteral(": ");
+
+        if (hasLocus() && locus() == value.length())
+            builder.appendLiteral("Unexpected end of attribute. ");
+
+        auto message = messageForStatus(status());
+        builder.append(message.first);
+        appendValue(builder, *this, value);
+        builder.append(message.second);
+    }
+    return builder.toString();
+}
+
+} // namespace blink