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- """Utilities for truncating assertion output.
- Current default behaviour is to truncate assertion explanations at
- terminal lines, unless running with an assertions verbosity level of at least 2 or running on CI.
- """
- from __future__ import annotations
- from _pytest.compat import running_on_ci
- from _pytest.config import Config
- from _pytest.nodes import Item
- DEFAULT_MAX_LINES = 8
- DEFAULT_MAX_CHARS = DEFAULT_MAX_LINES * 80
- USAGE_MSG = "use '-vv' to show"
- def truncate_if_required(explanation: list[str], item: Item) -> list[str]:
- """Truncate this assertion explanation if the given test item is eligible."""
- should_truncate, max_lines, max_chars = _get_truncation_parameters(item)
- if should_truncate:
- return _truncate_explanation(
- explanation,
- max_lines=max_lines,
- max_chars=max_chars,
- )
- return explanation
- def _get_truncation_parameters(item: Item) -> tuple[bool, int, int]:
- """Return the truncation parameters related to the given item, as (should truncate, max lines, max chars)."""
- # We do not need to truncate if one of conditions is met:
- # 1. Verbosity level is 2 or more;
- # 2. Test is being run in CI environment;
- # 3. Both truncation_limit_lines and truncation_limit_chars
- # .ini parameters are set to 0 explicitly.
- max_lines = item.config.getini("truncation_limit_lines")
- max_lines = int(max_lines if max_lines is not None else DEFAULT_MAX_LINES)
- max_chars = item.config.getini("truncation_limit_chars")
- max_chars = int(max_chars if max_chars is not None else DEFAULT_MAX_CHARS)
- verbose = item.config.get_verbosity(Config.VERBOSITY_ASSERTIONS)
- should_truncate = verbose < 2 and not running_on_ci()
- should_truncate = should_truncate and (max_lines > 0 or max_chars > 0)
- return should_truncate, max_lines, max_chars
- def _truncate_explanation(
- input_lines: list[str],
- max_lines: int,
- max_chars: int,
- ) -> list[str]:
- """Truncate given list of strings that makes up the assertion explanation.
- Truncates to either max_lines, or max_chars - whichever the input reaches
- first, taking the truncation explanation into account. The remaining lines
- will be replaced by a usage message.
- """
- # Check if truncation required
- input_char_count = len("".join(input_lines))
- # The length of the truncation explanation depends on the number of lines
- # removed but is at least 68 characters:
- # The real value is
- # 64 (for the base message:
- # '...\n...Full output truncated (1 line hidden), use '-vv' to show")'
- # )
- # + 1 (for plural)
- # + int(math.log10(len(input_lines) - max_lines)) (number of hidden line, at least 1)
- # + 3 for the '...' added to the truncated line
- # But if there's more than 100 lines it's very likely that we're going to
- # truncate, so we don't need the exact value using log10.
- tolerable_max_chars = (
- max_chars + 70 # 64 + 1 (for plural) + 2 (for '99') + 3 for '...'
- )
- # The truncation explanation add two lines to the output
- tolerable_max_lines = max_lines + 2
- if (
- len(input_lines) <= tolerable_max_lines
- and input_char_count <= tolerable_max_chars
- ):
- return input_lines
- # Truncate first to max_lines, and then truncate to max_chars if necessary
- if max_lines > 0:
- truncated_explanation = input_lines[:max_lines]
- else:
- truncated_explanation = input_lines
- truncated_char = True
- # We reevaluate the need to truncate chars following removal of some lines
- if len("".join(truncated_explanation)) > tolerable_max_chars and max_chars > 0:
- truncated_explanation = _truncate_by_char_count(
- truncated_explanation, max_chars
- )
- else:
- truncated_char = False
- if truncated_explanation == input_lines:
- # No truncation happened, so we do not need to add any explanations
- return truncated_explanation
- truncated_line_count = len(input_lines) - len(truncated_explanation)
- if truncated_explanation[-1]:
- # Add ellipsis and take into account part-truncated final line
- truncated_explanation[-1] = truncated_explanation[-1] + "..."
- if truncated_char:
- # It's possible that we did not remove any char from this line
- truncated_line_count += 1
- else:
- # Add proper ellipsis when we were able to fit a full line exactly
- truncated_explanation[-1] = "..."
- return [
- *truncated_explanation,
- "",
- f"...Full output truncated ({truncated_line_count} line"
- f"{'' if truncated_line_count == 1 else 's'} hidden), {USAGE_MSG}",
- ]
- def _truncate_by_char_count(input_lines: list[str], max_chars: int) -> list[str]:
- # Find point at which input length exceeds total allowed length
- iterated_char_count = 0
- for iterated_index, input_line in enumerate(input_lines):
- if iterated_char_count + len(input_line) > max_chars:
- break
- iterated_char_count += len(input_line)
- # Create truncated explanation with modified final line
- truncated_result = input_lines[:iterated_index]
- final_line = input_lines[iterated_index]
- if final_line:
- final_line_truncate_point = max_chars - iterated_char_count
- final_line = final_line[:final_line_truncate_point]
- truncated_result.append(final_line)
- return truncated_result
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