71 lines
2.1 KiB
Python
71 lines
2.1 KiB
Python
import shlex
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import subprocess
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from collections import namedtuple
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import bashlex
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NodeExecutionContext = namedtuple('NodeExecutionContext', ['environment', 'input'])
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def evaluate(value, environment):
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if not value:
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# empty string evaluates to empty string
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# (but trips up bashlex)
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return ''
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command_node = bashlex.parsesingle(value)
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if len(command_node.parts) != 1:
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raise ValueError('"%s" has too many parts' % value)
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value_word_node = command_node.parts[0]
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return evaluate_node(
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value_word_node,
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context=NodeExecutionContext(environment=environment, input=value)
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)
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def evaluate_node(node, context):
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if node.kind == 'word':
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return evaluate_word_node(node, context=context)
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elif node.kind == 'commandsubstitution':
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return evaluate_command_node(node.command, context=context)
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elif node.kind == 'parameter':
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return evaluate_parameter_node(node, context=context)
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else:
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raise ValueError('Unsupported bash construct: "%s"' % node.word)
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def evaluate_word_node(node, context):
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word_start = node.pos[0]
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word_end = node.pos[1]
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word_string = context.input[word_start:word_end]
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letters = list(word_string)
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for part in node.parts:
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part_start = part.pos[0] - word_start
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part_end = part.pos[1] - word_start
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# Set all the characters in the part to None
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for i in range(part_start, part_end):
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letters[i] = None
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letters[part_start] = evaluate_node(part, context=context)
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# remove the None letters and concat
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value = ''.join(l for l in letters if l is not None)
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# apply bash-like quotes/whitespace treatment
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return ' '.join(word.strip() for word in shlex.split(value))
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def evaluate_command_node(node, context):
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words = [evaluate_node(part, context=context) for part in node.parts]
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command = ' '.join(words)
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return subprocess.check_output(shlex.split(command), env=context.environment, universal_newlines=True)
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def evaluate_parameter_node(node, context):
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return context.environment.get(node.value, '')
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