fix: avoid measuring generated code. #1160

CHANGES.rst

@@ -30,6 +30,12 @@ Unreleased
 - Feature: The HTML report pages for Python source files now have a sticky
   header so the file name and controls are always visible.
 
+- Fix: more generated code is now excluded from measurement.  Code such as
+  `attrs`_ boilerplate, or doctest code, was being measured though the
+  synthetic line numbers meant they were never reported.  Once Cython was
+  involved though, the generated .so files were parsed as Python, raising
+  syntax errors, as reported in `issue 1160`_.  This is now fixed.
+
 - Fix: When sorting human-readable names, numeric components are sorted
   correctly: file10.py will appear after file9.py.  This applies to file names,
   module names, environment variables, and test contexts.
@@ -41,6 +47,8 @@ Unreleased
 
 .. _issue 553: https://github.com/nedbat/coveragepy/issues/553
 .. _issue 840: https://github.com/nedbat/coveragepy/issues/840
+.. _issue 1160: https://github.com/nedbat/coveragepy/issues/1160
+.. _attrs: https://www.attrs.org/
 
 
 .. _changes_602:

coverage/disposition.py

@@ -30,6 +30,8 @@ def disposition_debug_msg(disp):
     """Make a nice debug message of what the FileDisposition is doing."""
     if disp.trace:
         msg = f"Tracing {disp.original_filename!r}"
+        if disp.original_filename != disp.source_filename:
+            msg += f" as {disp.source_filename!r}"
         if disp.file_tracer:
             msg += ": will be traced by %r" % disp.file_tracer
     else:

coverage/inorout.py

@@ -317,6 +317,9 @@ def nope(disp, reason):
             disp.reason = reason
             return disp
 
+        if original_filename.startswith('<'):
+            return nope(disp, "not a real original file name")
+
         if frame is not None:
             # Compiled Python files have two file names: frame.f_code.co_filename is
             # the file name at the time the .pyc was compiled.  The second name is

tests/test_oddball.py

@@ -393,7 +393,13 @@ class DoctestTest(CoverageTest):
     """Tests invoked with doctest should measure properly."""
 
     def test_doctest(self):
-        self.check_coverage('''\
+        # Doctests used to be traced, with their line numbers credited to the
+        # file they were in.  Below, one of the doctests has four lines (1-4),
+        # which would incorrectly claim that lines 1-4 of the file were
+        # executed.  In this file, line 2 is not executed.
+        self.make_file("the_doctest.py", '''\
+            if "x" in "abc":
+                print("hello")
             def return_arg_or_void(arg):
                 """If <arg> is None, return "Void"; otherwise return <arg>
 
@@ -403,6 +409,11 @@ def return_arg_or_void(arg):
                 'arg'
                 >>> return_arg_or_void("None")
                 'None'
+                >>> if "x" in "xyz":                # line 1
+                ...   if "a" in "aswed":            # line 2
+                ...      if "a" in "abc":           # line 3
+                ...         return_arg_or_void(12)  # line 4
+                12
                 """
                 if arg is None:
                     return "Void"
@@ -411,8 +422,13 @@ def return_arg_or_void(arg):
 
             import doctest, sys
             doctest.testmod(sys.modules[__name__])  # we're not __main__ :(
-            ''',
-            [1, 11, 12, 14, 16, 17], "")
+            ''')
+        cov = coverage.Coverage()
+        self.start_import_stop(cov, "the_doctest")
+        data = cov.get_data()
+        assert len(data.measured_files()) == 1
+        lines = data.lines(data.measured_files().pop())
+        assert lines == [1, 3, 18, 19, 21, 23, 24]
 
 
 class GettraceTest(CoverageTest):