Add thorough test, and fix found issues in traceback.py

python · miss-islington · May 15, 2020 · May 13, 2020 · May 13, 2020 · May 13, 2020
commit 6df7662ca5f0fa63d31986f56b3d7dd33889be0e
diff --git a/Lib/test/test_traceback.py b/Lib/test/test_traceback.py
@@ -80,12 +80,11 @@ def test_bad_indentation(self):
         self.assertIn("^", err[2])
         self.assertEqual(err[1].find(")") + 1, err[2].find("^"))
 
+        # No caret for "unexpected indent"
         err = self.get_exception_format(self.syntax_error_bad_indentation2,
                                         IndentationError)
-        self.assertEqual(len(err), 4)
+        self.assertEqual(len(err), 3)
         self.assertEqual(err[1].strip(), "print(2)")
-        self.assertIn("^", err[2])
-        self.assertEqual(err[1].find("p"), err[2].find("^"))
 
     def test_base_exception(self):
         # Test that exceptions derived from BaseException are formatted right
@@ -679,6 +678,29 @@ def test_message_none(self):
         err = self.get_report(Exception(''))
         self.assertIn('Exception\n', err)
 
+    def test_syntax_error_various_offsets(self):
+        print()
+        for offset in range(-5, 10):
+            for add in [0, 2]:
+                text = " "*add + "text%d" % offset
+                expected = ['  File "file.py", line 1']
+                if offset < 1:
+                    expected.append("    %s" % text.lstrip())
+                elif offset <= 6:
+                    expected.append("    %s" % text.lstrip())
+                    expected.append("    %s^" % (" "*(offset-1)))
+                else:
+                    expected.append("    %s" % text.lstrip())
+                    expected.append("    %s^" % (" "*5))
+                expected.append("SyntaxError: msg")
+                expected.append("")
+                err = self.get_report(SyntaxError("msg", ("file.py", 1, offset+add, text)))
+                exp = "\n".join(expected)
+                if exp != err:
+                    print(f">>> offset={offset}; add={add}; text={text!r}")
+                    print(err)
+                self.assertEqual(exp, err)
+
 
 class PyExcReportingTests(BaseExceptionReportingTests, unittest.TestCase):
     #

diff --git a/Lib/traceback.py b/Lib/traceback.py
@@ -579,17 +579,20 @@ def _format_syntax_error(self, stype):
         lineno = str(self.lineno) or '?'
         yield '  File "{}", line {}\n'.format(filename, lineno)
 
-        badline = self.text
-        offset = self.offset
-        if badline is not None:
-            yield '    {}\n'.format(badline.strip())
-            if offset is not None and offset >= 1:
-                caretspace = badline.rstrip('\n')
-                # Convert to 0-based offset, and clip to text length
-                offset = min(len(caretspace), offset - 1)
-                caretspace = caretspace[:offset].lstrip()
+        text = self.text
+        if text is not None:
+            # text  = "   foo\n"
+            # rtext = "   foo"
+            # ltext =    "foo"
+            rtext = text.rstrip('\n')
+            ltext = rtext.lstrip(' \n\f')
+            spaces = len(rtext) - len(ltext)
+            yield '    {}\n'.format(ltext)
+            # Convert 1-based column offset to 0-based index into stripped text
+            caret = (self.offset or 0) - 1 - spaces
+            if caret >= 0:
                 # non-space whitespace (likes tabs) must be kept for alignment
-                caretspace = ((c if c.isspace() else ' ') for c in caretspace)
+                caretspace = ((c if c.isspace() else ' ') for c in ltext[:caret])
                 yield '    {}^\n'.format(''.join(caretspace))
         msg = self.msg or "<no detail available>"
         yield "{}: {}\n".format(stype, msg)