debug: a tool for extracting test code snippets

1 files changed, 73 insertions, 0 deletions

diff --git a/lab/extract_code.py b/lab/extract_code.py
new file mode 100644
index 00000000..ec077af7
--- /dev/null
+++ b/lab/extract_code.py
@@ -0,0 +1,73 @@
+# Licensed under the Apache License: http://www.apache.org/licenses/LICENSE-2.0
+# For details: https://github.com/nedbat/coveragepy/blob/master/NOTICE.txt
+
+"""
+Use this to copy some indented code from the coverage.py test suite into a
+standalone file for deeper testing, or writing bug reports.
+
+Give it a file name and a line number, and it will find the indentend
+multiline string containing that line number, and output the dedented
+contents of the string.
+
+If tests/test_arcs.py has this (partial) content::
+
+    1626	    @pytest.mark.skipif(
+    1627	        (3, 11, 0, "alpha", 4) <= env.PYVERSION,
+    1628	        reason="avoid a 3.11 bug: https://bugs.python.org/issue46389",
+    1629	    )
+    1630	    def test_partial_generators(self):
+    1631	        # https://github.com/nedbat/coveragepy/issues/475
+    1632	        # Line 2 is executed completely.
+    1633	        # Line 3 is started but not finished, because zip ends before it finishes.
+    1634	        # Line 4 is never started.
+    1635	        cov = self.check_coverage('''\
+    1636	            def f(a, b):
+    1637	                c = (i for i in a)          # 2
+    1638	                d = (j for j in b)          # 3
+    1639	                e = (k for k in b)          # 4
+    1640	                return dict(zip(c, d))
+    1641
+    1642	            f(['a', 'b'], [1, 2, 3])
+    1643	            ''',
+    1644	            arcz=".1 17 7.  .2 23 34 45 5.  -22 2-2  -33 3-3  -44 4-4",
+    1645	            arcz_missing="3-3 -44 4-4",
+    1646	        )
+
+then you can do::
+
+    % python lab/extract_code.py tests/test_arcs.py 1637
+    def f(a, b):
+        c = (i for i in a)          # 2
+        d = (j for j in b)          # 3
+        e = (k for k in b)          # 4
+        return dict(zip(c, d))
+
+    f(['a', 'b'], [1, 2, 3])
+    %
+
+"""
+
+import sys
+import textwrap
+
+fname, lineno = sys.argv[1:]
+lineno = int(lineno)
+
+with open(fname) as code_file:
+    lines = ["", *code_file]
+
+# Find opening triple-quote
+for start in range(lineno, 0, -1):
+    line = lines[start]
+    if "'''" in line or '"""' in line:
+        break
+
+for end in range(lineno+1, len(lines)):
+    line = lines[end]
+    if "'''" in line or '"""' in line:
+        break
+
+code = "".join(lines[start+1: end])
+code = textwrap.dedent(code)
+
+print(code, end="")