Make coverage.py handle "stringsource" better by making it clear that it is...

Make coverage.py handle "stringsource" better by making it clear that it is not a file name (GH-4440)

Having a code object with `co_filename` set to just "stringsource" (e.g. when using memory views or auto-pickling), causes coverage.py to think that "stringsource" is a relative path to an actual file. The convention is to wrap such fake paths with angle brackets, which coverage.py correctly recognizes.

You will recognize this as the following error, e.g. when running "coverage html":
    No source for code: '.../stringsource'.
    Aborting report output, consider using -i.

Cython/Compiler/Scanning.py

@@ -277,7 +277,7 @@ class StringSourceDescriptor(SourceDescriptor):
     get_error_description = get_description
 
     def get_filenametable_entry(self):
-        return "stringsource"
+        return "<stringsource>"
 
     def __hash__(self):
         return id(self)

tests/run/coverage_cmd.srctree

@@ -29,43 +29,59 @@ plugins = Cython.Coverage
 ######## pkg/coverage_test_py.py ########
 # cython: linetrace=True
 # distutils: define_macros=CYTHON_TRACE=1
+import cython
+
 
 def func1(a, b):
-    x = 1               #  5
-    c = func2(a) + b    #  6
-    return x + c        #  7
+    x = 1               #  7
+    c = func2(a) + b    #  8
+    return x + c        #  9
 
 
 def func2(a):
-    return a * 2        # 11
+    return a * 2        # 13
 
 
 def func3(a):
-    x = 1               # 15
+    x = 1               # 17
     a *= 2              #     # pragma: no cover
     a += x              #
-    return a * 42       # 18  # pragma: no cover
+    return a * 42       # 20  # pragma: no cover
+
+
+@cython.cclass
+class A:
+    def meth(self):
+        return 1        # 26
 
 
 ######## pkg/coverage_test_pyx.pyx ########
 # cython: linetrace=True
 # distutils: define_macros=CYTHON_TRACE=1
 
+
+
 def func1(int a, int b):
-    cdef int x = 1      #  5
-    c = func2(a) + b    #  6
-    return x + c        #  7
+    cdef int x = 1      #  7
+    c = func2(a) + b    #  8
+    return x + c        #  9
 
 
 def func2(int a):
-    return a * 2        # 11
+    return a * 2        # 13
 
 
 def func3(int a):
-    cdef int x = 1      # 15
+    cdef int x = 1      # 17
     a *= 2              #     # pragma: no cover
     a += x              #
-    return a * 42       # 18  # pragma: no cover
+    return a * 42       # 20  # pragma: no cover
+
+
+
+cdef class A:
+    def meth(self):
+        return 1        # 26
 
 
 ######## coverage_test_include_pyx.pyx ########
@@ -110,6 +126,9 @@ def run_coverage(module):
     assert module.func2(2) == 2 * 2
     if '_include_' in module_name:
         assert module.main_func(2) == (2 * 3) + ((2 * 2) + 4 + 1) + (2 * 2)
+    assert module.A().meth() == 1
+
+
 
 
 if __name__ == '__main__':
@@ -186,9 +205,10 @@ def run_xml_report():
         )
 
     report = files['pkg/coverage_test_pyx.pyx']
-    assert report[5] > 0, report
-    assert report[6] > 0, report
     assert report[7] > 0, report
+    assert report[8] > 0, report
+    assert report[9] > 0, report
+    assert report[26] > 0, report
 
 
 def run_json_report():
@@ -210,8 +230,8 @@ def run_json_report():
         summary = report['summary']
         assert summary['missing_lines'] == 2, summary
         assert summary['excluded_lines'] == 2, summary
-        assert report['missing_lines'] == [15, 17], report
-        assert report['excluded_lines'] == [16, 18], report
+        assert report['missing_lines'] == [17, 19], report
+        assert report['excluded_lines'] == [18, 20], report
 
         assert not frozenset(
             report['missing_lines'] + report['excluded_lines']
@@ -246,13 +266,14 @@ def run_html_report():
         missing = report["mis"]
         excluded = report["exc"]
         assert executed, (filename, report)
-        assert 5 in executed, executed
-        assert 6 in executed, executed
         assert 7 in executed, executed
-        assert 15 in missing, missing
-        assert 16 in excluded, excluded
+        assert 8 in executed, executed
+        assert 9 in executed, executed
+        assert 26 in executed, executed
         assert 17 in missing, missing
         assert 18 in excluded, excluded
+        assert 19 in missing, missing
+        assert 20 in excluded, excluded
 
 
 if __name__ == '__main__':