[processing] Fix escaping of srcnodata argument in Build Virtual Raster

alg

python/plugins/processing/algs/gdal/GdalUtils.py

@@ -255,7 +255,8 @@ class GdalUtils:
         for s in strList:
             if not isinstance(s, str):
                 s = str(s)
-            if s and s[0] != '-' and any(c in s for c in escChars):
+            # don't escape if command starts with - and isn't a negative number, e.g. -9999
+            if s and re.match(r'^([^-]|-\d)', s) and any(c in s for c in escChars):
                 escaped = '"' + s.replace('\\', '\\\\').replace('"', '"""') \
                           + '"'
             else:

python/plugins/processing/algs/gdal/buildvrt.py

@@ -196,7 +196,8 @@ class buildvrt(GdalAlgorithm):
 
         if self.SRC_NODATA in parameters and parameters[self.SRC_NODATA] not in (None, ''):
             nodata = self.parameterAsString(parameters, self.SRC_NODATA, context)
-            arguments.append('-srcnodata "{}"'.format(nodata))
+            arguments.append('-srcnodata')
+            arguments.append(nodata)
 
         if self.EXTRA in parameters and parameters[self.EXTRA] not in (None, ''):
             extra = self.parameterAsString(parameters, self.EXTRA, context)

python/plugins/processing/tests/GdalAlgorithmsGeneralTest.py

@@ -339,6 +339,7 @@ class TestGdalAlgorithms(unittest.TestCase):
 
     def testEscapeAndJoin(self):
         self.assertEqual(GdalUtils.escapeAndJoin([1, "a", "a b", "a&b", "a(b)", ";"]), '1 a "a b" "a&b" "a(b)" ";"')
+        self.assertEqual(GdalUtils.escapeAndJoin([1, "-srcnodata", "--srcnodata", "-9999 9999"]), '1 -srcnodata --srcnodata "-9999 9999"')
 
 
 if __name__ == '__main__':

python/plugins/processing/tests/GdalAlgorithmsRasterTest.py

@@ -2606,7 +2606,7 @@ class TestGdalRasterAlgorithms(unittest.TestCase, AlgorithmsTestBase.AlgorithmsT
             cmd[1] = t[:t.find('-input_file_list') + 17] + t[t.find('buildvrtInputFiles.txt'):]
             self.assertEqual(cmd,
                              ['gdalbuildvrt',
-                              '-resolution average -separate -r nearest -srcnodata "-9999" ' +
+                              '-resolution average -separate -r nearest -srcnodata -9999 ' +
                               '-input_file_list buildvrtInputFiles.txt ' +
                               outdir + '/check.vrt'])