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import re
from typing import Mapping, Match, Optional, Sequence
# match $identifier or ${identifier} and replace with value in env
# If this identifier is at the beginning of whitespace on a line
# and its value is a list then it is treated as
# block substitution by indenting to that depth and putting each element
# of the list on its own line
# if the identifier is on a line starting with non-whitespace and a list
# then it is comma separated ${,foo} will insert a comma before the list
# if this list is not empty and ${foo,} will insert one after.
class CodeTemplate:
substitution_str = r"(^[^\n\S]*)?\$([^\d\W]\w*|\{,?[^\d\W]\w*\,?})"
substitution = re.compile(substitution_str, re.MULTILINE)
pattern: str
filename: str
@staticmethod
def from_file(filename: str) -> "CodeTemplate":
with open(filename) as f:
return CodeTemplate(f.read(), filename)
def __init__(self, pattern: str, filename: str = "") -> None:
self.pattern = pattern
self.filename = filename
def substitute(
self, env: Optional[Mapping[str, object]] = None, **kwargs: object
) -> str:
if env is None:
env = {}
def lookup(v: str) -> object:
assert env is not None
return kwargs[v] if v in kwargs else env[v]
def indent_lines(indent: str, v: Sequence[object]) -> str:
return "".join(
[indent + l + "\n" for e in v for l in str(e).splitlines()]
).rstrip()
def replace(match: Match[str]) -> str:
indent = match.group(1)
key = match.group(2)
comma_before = ""
comma_after = ""
if key[0] == "{":
key = key[1:-1]
if key[0] == ",":
comma_before = ", "
key = key[1:]
if key[-1] == ",":
comma_after = ", "
key = key[:-1]
v = lookup(key)
if indent is not None:
if not isinstance(v, list):
v = [v]
return indent_lines(indent, v)
elif isinstance(v, list):
middle = ", ".join([str(x) for x in v])
if len(v) == 0:
return middle
return comma_before + middle + comma_after
else:
return str(v)
return self.substitution.sub(replace, self.pattern)
if __name__ == "__main__":
c = CodeTemplate(
"""\
int foo($args) {
$bar
$bar
$a+$b
}
int commatest(int a${,stuff})
int notest(int a${,empty,})
"""
)
print(
c.substitute(
args=["hi", 8],
bar=["what", 7],
a=3,
b=4,
stuff=["things...", "others"],
empty=[],
)
)