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51 lines
1.9 KiB
Python
51 lines
1.9 KiB
Python
"""Common template rendering utility."""
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import re
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from typing import Any, Dict
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def render_template(template_str: str, template_var_mapping: Dict[str, Any]) -> str: # noqa: C901 – complex but self-contained
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"""Replace template placeholders in *template_str* with values from *template_var_mapping*.
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Supported syntax:
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* ``{{ variable_name }}``
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* ``{{ variable_name | fallback }}``
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* ``{{ variable_name | fallback:default_value }}``
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If the variable is undefined and a *fallback* filter is specified the value
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of *default_value* (or the *variable_name* itself if no default is given)
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is used instead.
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"""
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if not template_str:
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return template_str
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# Regex matches e.g. ``{{ name }}``, ``{{ name | fallback }}``, ``{{ name | fallback:John }}``
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pattern = r"\{\{\s*([^|\s}]+)(?:\s*\|\s*([^:}]+)(?::([^}]+))?)?\s*\}\}"
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def _replace(match: re.Match[str]) -> str: # type: ignore[type-arg]
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variable_name = match.group(1).strip()
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filter_name = match.group(2).strip() if match.group(2) else None
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filter_value = match.group(3).strip() if match.group(3) else None
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# Pull value from context
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value = template_var_mapping.get(variable_name)
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# Apply filters
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if filter_name == "fallback":
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if value is None or value == "":
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# Use explicit default value or a title-cased variable name.
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value = (
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filter_value if filter_value is not None else variable_name.title()
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)
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# Convert *None* to an empty string so that re.sub replacement works.
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return str(value) if value is not None else ""
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# Replace template variables
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result = re.sub(pattern, _replace, template_str)
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# Handle line breaks (convert literal \n to actual newlines)
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result = result.replace("\\n", "\n")
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return result
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