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"""Read single-line dotenv values without evaluating shell expressions."""
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import re
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ENV_ASSIGNMENT = re.compile(r"^\s*(?:export\s+)?([A-Za-z_][A-Za-z0-9_]*)\s*=\s*(.*)$")
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def read_env(path):
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    values = {}
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    if path.exists():
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        for number, line in enumerate(path.read_text().splitlines(), 1):
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            if not line.strip() or line.lstrip().startswith("#"):
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                continue
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            match = ENV_ASSIGNMENT.fullmatch(line)
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            if not match:
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                raise SystemExit(f"{path.name}:{number}: expected NAME=value")
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            key, raw = match.groups()
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            if key in values:
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                raise SystemExit(f"{path.name}:{number}: duplicate {key}")
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            if raw.startswith(("'", '"', "`")):
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                quote = raw[0]
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                end = raw.find(quote, 1)
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                if end < 0 or (raw[end + 1:].strip() and not raw[end + 1:].lstrip().startswith("#")):
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                    raise SystemExit(
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                        f"{path.name}:{number}: wrap {key} in a quote style absent from its value"
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                    )
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                value = raw[1:end]
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                if quote == '"':
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                    value = value.replace("\\n", "\n").replace("\\r", "\r")
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            else:
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                value = raw.split("#", 1)[0].strip()
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            if any(character in value for character in ("\n", "\r", "\0")):
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                raise SystemExit(f"{path.name}:{number}: {key} must be a single-line value")
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            values[key] = value
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    return values
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def env_value(key, value):
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    """Quote a literal value identically for this reader, Node and Wrangler."""
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    if any(character in value for character in ("\n", "\r", "\0")):
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        raise SystemExit(f"{key} must be a single-line value")
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    for quote in ("'", '"', "`"):
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        if quote in value:
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            continue
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        if quote == '"' and ("\\n" in value or "\\r" in value):
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            continue
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        return f"{quote}{value}{quote}"
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    raise SystemExit(f"{key} needs a value that can be wrapped in one dotenv quote style")