When a remote SVG is requested but fails, use the missing SVG icon

as an indicator for users that something went wrong

This was previously only used for replies with incorrect mime
types or authentication errors, but it meant that an incorrect
SVG url would silently result in no symbols rendered.

Also add unit tests for fetching remote svg images

(cherry-picked from 7794144)

src/core/symbology/qgssvgcache.cpp

@@ -433,10 +433,9 @@ QByteArray QgsSvgCache::getImageData( const QString &path ) const
 
     if ( reply->error() != QNetworkReply::NoError )
     {
-      QgsMessageLog::logMessage( tr( "SVG request failed [error: %1 - url: %2]" ).arg( reply->errorString(), reply->url().toString() ), tr( "SVG" ) );
-
+      QgsMessageLog::logMessage( tr( "SVG request failed [error: %1 - url: %2]" ).arg( reply->errorString(), path ), tr( "SVG" ) );
       reply->deleteLater();
-      return QByteArray();
+      return mMissingSvg;
     }
 
     QVariant redirect = reply->attribute( QNetworkRequest::RedirectionTargetAttribute );

tests/src/python/CMakeLists.txt

@@ -149,6 +149,7 @@ ADD_PYTHON_TEST(PyQgsReport test_qgsreport.py)
 ADD_PYTHON_TEST(PyQgsRulebasedRenderer test_qgsrulebasedrenderer.py)
 ADD_PYTHON_TEST(PyQgsSingleSymbolRenderer test_qgssinglesymbolrenderer.py)
 ADD_PYTHON_TEST(PyQgsShapefileProvider test_provider_shapefile.py)
+ADD_PYTHON_TEST(PyQgsSvgCache test_qgssvgcache.py)
 ADD_PYTHON_TEST(PyQgsSymbolButton test_qgssymbolbutton.py)
 ADD_PYTHON_TEST(PyQgsTabfileProvider test_provider_tabfile.py)
 ADD_PYTHON_TEST(PyQgsTabWidget test_qgstabwidget.py)

tests/src/python/test_qgssvgcache.py

@@ -0,0 +1,95 @@
+# -*- coding: utf-8 -*-
+"""QGIS Unit tests for QgsSvgCache.
+
+.. note:: This program is free software; you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation; either version 2 of the License, or
+(at your option) any later version.
+"""
+__author__ = '(C) 2018 by Nyall Dawson'
+__date__ = '29/03/2018'
+__copyright__ = 'Copyright 2018, The QGIS Project'
+# This will get replaced with a git SHA1 when you do a git archive
+__revision__ = '$Format:%H$'
+
+import qgis  # NOQA
+
+import os
+import socketserver
+import threading
+import http.server
+from qgis.PyQt.QtCore import QDir
+from qgis.PyQt.QtGui import QColor
+
+from qgis.core import (QgsSvgCache, QgsRenderChecker, QgsApplication)
+from qgis.testing import start_app, unittest
+from utilities import unitTestDataPath
+
+start_app()
+TEST_DATA_DIR = unitTestDataPath()
+
+
+class TestQgsSvgCache(unittest.TestCase):
+
+    @classmethod
+    def setUpClass(cls):
+        # Bring up a simple HTTP server, for remote SVG tests
+        os.chdir(unitTestDataPath() + '')
+        handler = http.server.SimpleHTTPRequestHandler
+
+        cls.httpd = socketserver.TCPServer(('localhost', 0), handler)
+        cls.port = cls.httpd.server_address[1]
+
+        cls.httpd_thread = threading.Thread(target=cls.httpd.serve_forever)
+        cls.httpd_thread.setDaemon(True)
+        cls.httpd_thread.start()
+
+    def setUp(self):
+        self.report = "<h1>Python QgsSvgCache Tests</h1>\n"
+
+    def tearDown(self):
+        report_file_path = "%s/qgistest.html" % QDir.tempPath()
+        with open(report_file_path, 'a') as report_file:
+            report_file.write(self.report)
+
+    def testRemoteSVG(self):
+        """Test fetching remote svg."""
+        url = 'http://localhost:{}/qgis_local_server/sample_svg.svg'.format(str(TestQgsSvgCache.port))
+        image, in_cache = QgsApplication.svgCache().svgAsImage(url, 100, fill=QColor(0, 0, 0), stroke=QColor(0, 0, 0), strokeWidth=0.1, widthScaleFactor=1)
+        self.assertTrue(self.imageCheck('Remote SVG', 'remote_svg', image))
+
+    def testRemoteSvgAsText(self):
+        """Test fetching remote svg with text mime format - e.g. github raw svgs"""
+        url = 'http://localhost:{}/qgis_local_server/svg_as_text.txt'.format(str(TestQgsSvgCache.port))
+        image, in_cache = QgsApplication.svgCache().svgAsImage(url, 100, fill=QColor(0, 0, 0), stroke=QColor(0, 0, 0), strokeWidth=0.1, widthScaleFactor=1)
+        self.assertTrue(self.imageCheck('Remote SVG as Text', 'remote_svg', image))
+
+    def testRemoteSvgBadMime(self):
+        """Test fetching remote svg with bad mime type"""
+        url = 'http://localhost:{}/qgis_local_server/logo.png'.format(str(TestQgsSvgCache.port))
+        image, in_cache = QgsApplication.svgCache().svgAsImage(url, 100, fill=QColor(0, 0, 0), stroke=QColor(0, 0, 0), strokeWidth=0.1, widthScaleFactor=1)
+        self.assertTrue(self.imageCheck('Remote SVG bad MIME type', 'bad_svg', image))
+
+    def testRemoteSvgMissing(self):
+        """Test fetching remote svg with bad url"""
+        url = 'http://localhost:{}/qgis_local_server/xxx.svg'.format(str(TestQgsSvgCache.port))  # oooo naughty
+        image, in_cache = QgsApplication.svgCache().svgAsImage(url, 100, fill=QColor(0, 0, 0), stroke=QColor(0, 0, 0), strokeWidth=0.1, widthScaleFactor=1)
+        self.assertTrue(self.imageCheck('Remote SVG missing', 'bad_svg', image))
+
+    def imageCheck(self, name, reference_image, image):
+        self.report += "<h2>Render {}</h2>\n".format(name)
+        temp_dir = QDir.tempPath() + '/'
+        file_name = temp_dir + 'svg_' + name + ".png"
+        image.save(file_name, "PNG")
+        checker = QgsRenderChecker()
+        checker.setControlPathPrefix("svg_cache")
+        checker.setControlName("expected_" + reference_image)
+        checker.setRenderedImage(file_name)
+        checker.setColorTolerance(2)
+        result = checker.compareImages(name, 20)
+        self.report += checker.report()
+        print((self.report))
+        return result
+
+if __name__ == '__main__':
+    unittest.main()