115 lines
4.3 KiB
Python
115 lines
4.3 KiB
Python
"""Utilities for truncating assertion output.
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Current default behaviour is to truncate assertion explanations at
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~8 terminal lines, unless running in "-vv" mode or running on CI.
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"""
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from typing import List
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from typing import Optional
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from _pytest.assertion import util
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from _pytest.nodes import Item
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DEFAULT_MAX_LINES = 8
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DEFAULT_MAX_CHARS = 8 * 80
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USAGE_MSG = "use '-vv' to show"
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def truncate_if_required(
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explanation: List[str], item: Item, max_length: Optional[int] = None
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) -> List[str]:
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"""Truncate this assertion explanation if the given test item is eligible."""
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if _should_truncate_item(item):
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return _truncate_explanation(explanation)
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return explanation
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def _should_truncate_item(item: Item) -> bool:
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"""Whether or not this test item is eligible for truncation."""
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verbose = item.config.option.verbose
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return verbose < 2 and not util.running_on_ci()
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def _truncate_explanation(
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input_lines: List[str],
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max_lines: Optional[int] = None,
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max_chars: Optional[int] = None,
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) -> List[str]:
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"""Truncate given list of strings that makes up the assertion explanation.
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Truncates to either 8 lines, or 640 characters - whichever the input reaches
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first, taking the truncation explanation into account. The remaining lines
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will be replaced by a usage message.
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"""
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if max_lines is None:
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max_lines = DEFAULT_MAX_LINES
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if max_chars is None:
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max_chars = DEFAULT_MAX_CHARS
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# Check if truncation required
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input_char_count = len("".join(input_lines))
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# The length of the truncation explanation depends on the number of lines
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# removed but is at least 68 characters:
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# The real value is
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# 64 (for the base message:
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# '...\n...Full output truncated (1 line hidden), use '-vv' to show")'
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# )
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# + 1 (for plural)
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# + int(math.log10(len(input_lines) - max_lines)) (number of hidden line, at least 1)
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# + 3 for the '...' added to the truncated line
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# But if there's more than 100 lines it's very likely that we're going to
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# truncate, so we don't need the exact value using log10.
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tolerable_max_chars = (
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max_chars + 70 # 64 + 1 (for plural) + 2 (for '99') + 3 for '...'
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)
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# The truncation explanation add two lines to the output
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tolerable_max_lines = max_lines + 2
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if (
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len(input_lines) <= tolerable_max_lines
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and input_char_count <= tolerable_max_chars
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):
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return input_lines
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# Truncate first to max_lines, and then truncate to max_chars if necessary
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truncated_explanation = input_lines[:max_lines]
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truncated_char = True
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# We reevaluate the need to truncate chars following removal of some lines
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if len("".join(truncated_explanation)) > tolerable_max_chars:
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truncated_explanation = _truncate_by_char_count(
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truncated_explanation, max_chars
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)
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else:
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truncated_char = False
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truncated_line_count = len(input_lines) - len(truncated_explanation)
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if truncated_explanation[-1]:
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# Add ellipsis and take into account part-truncated final line
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truncated_explanation[-1] = truncated_explanation[-1] + "..."
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if truncated_char:
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# It's possible that we did not remove any char from this line
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truncated_line_count += 1
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else:
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# Add proper ellipsis when we were able to fit a full line exactly
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truncated_explanation[-1] = "..."
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return truncated_explanation + [
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"",
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f"...Full output truncated ({truncated_line_count} line"
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f"{'' if truncated_line_count == 1 else 's'} hidden), {USAGE_MSG}",
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]
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def _truncate_by_char_count(input_lines: List[str], max_chars: int) -> List[str]:
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# Find point at which input length exceeds total allowed length
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iterated_char_count = 0
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for iterated_index, input_line in enumerate(input_lines):
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if iterated_char_count + len(input_line) > max_chars:
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break
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iterated_char_count += len(input_line)
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# Create truncated explanation with modified final line
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truncated_result = input_lines[:iterated_index]
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final_line = input_lines[iterated_index]
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if final_line:
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final_line_truncate_point = max_chars - iterated_char_count
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final_line = final_line[:final_line_truncate_point]
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truncated_result.append(final_line)
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return truncated_result
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