Crash report

Four separate small code samples break doctest because a newline is misinterpreted.
In all four code samples, the failure follows the newline string, "\n", whether it appears
as a string literal or is assigned to a variable.

CONTEXT 1

• A newline character in a literal string: "\n",
• in an __init__(),
• in a class,
• that is in a docstring,
• that is inside an outermost class

CAUSES doctest.testmod() to

1. raise a ValueError exception,
2. diagnose that line 10 of the docstring has inconsistent leading whitespace: '",' -- when there is no inconsistent leading whitespace in the file --
3. display a Traceback stack,
4. return to the shell prompt with status code 1.

TRACEBACK, context 1

Runable code sample 1 contains a traceback.

Error messages, context 1

• ValueError: line 10 of the docstring for main.F has inconsistent leading whitespace: '",'
• returned to shell prompt with status code 1.

CONTEXT 2

• Assigning a newline character in a literal string to a variable
• in an __init__(),
• in a class,
• that is in a docstring,
• that is inside an outermost class

CAUSES doctest.testmod() to

1. raise a ValueError exception,
2. -- NOTE THE LINE NUMBER CHANGE FROM CONTEXT 1--
3. diagnose that line 5 of the docstring has inconsistent leading whitespace: '",' -- when there is no inconsistent leading whitespace in the file --
4. display a Traceback stack,
5. return to the shell prompt with status code 1.

TRACEBACK, context 2

Runable code sample 2 contains a traceback.

Error messages, context 2

• ValueError: line 5 of the docstring for main.F has inconsistent leading whitespace: '"'
• returned to shell prompt with status code 1.

CONTEXT 3

• A newline character in a literal string ("\n"),
• in a function,
• that is in a docstring

CAUSES doctest.testmod() to

1. incorrectly interpret string literal "\n" as a line break,
2. try a test that was not requested,
3. incorrectly expect the test to produce the bottom of function in_it(),
4. raise a SyntaxError exception,
5. incorrectly detect that line 9 of the docstring has an unterminated string literal -- although there are no unterminated string literals in the file --
6. display a Traceback stack,
7. return to the shell prompt with status code 0, as if nothing bad happened.

TRACEBACK, context 3

Runable code sample 3 contains both the try/expecting pair and the traceback.

Error messages, context 3

• SyntaxError: unterminated string literal (detected at line 9)
• returned to shell prompt with status code 0.

CONTEXT 4

• Assigning a newline character in a literal string to a variable
• in a function,
• that is in a docstring

CAUSES doctest.testmod() to

1. incorrectly interpret string literal "\n" as a line break,
2. try a test that was not requested,
3. incorrectly expect the test to produce the bottom of function in_it(),
4. raise a SyntaxError exception,
5. -- NOTE THE LINE NUMBER CHANGE FROM CONTEXT 3--
6. incorrectly detect that line 4 of the docstring has an unterminated string literal -- although there are no unterminated string literals in the file --
7. display a Traceback stack,
8. return to the shell prompt with status code 0, as if nothing bad happened.

TRACEBACK, context 4

Runable code sample 4 contains both the try/expecting pair and the traceback.

Error messages, context 4

• SyntaxError: unterminated string literal (detected at line 4)
• returned to shell prompt with status code 0.

My environment

• CPython versions tested on: Python 3.11.2 (main, Mar 24 2023, 00:28:48) [Clang 14.0.0 (clang-1400.0.29.202)]
• Operating system and architecture: macOS 12.6.5, Intel Core i9

codesample1.tgz
codesample2.tgz
codesample3.tgz
codesample4.tgz