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132 lines
4.5 KiB
132 lines
4.5 KiB
# coding=utf-8
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"""
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A module for creating and sanitizing identifiers
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"""
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import itertools
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import logging
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import re
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import unicodedata
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from keyword import iskeyword
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from string import ascii_uppercase
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import six
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log = logging.getLogger(__name__)
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_invalid_ident_char_re = re.compile(r'[^a-zA-Z0-9_]+')
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_invalid_ident_start_re = re.compile(r'^(?=[0-9_])')
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def _sanitize_ident(ident, prefix="c", capitalize=False):
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"""
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Helper for pick_ident, which given a suggested identifier, massages it to ensure it's valid for
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python (and sqlite). In particular, leaves only alphanumeric characters, and prepends `prefix`
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if it doesn't start with a letter.
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Returns empty string if there are no valid identifier characters, so consider using as
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(_sanitize_ident(...) or "your_default").
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"""
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ident = u"" if ident is None else six.text_type(ident)
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# https://stackoverflow.com/a/517974/2482744
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# Separate out combining characters (e.g. accents)
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ident = unicodedata.normalize('NFKD', ident)
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# then remove them completely
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# This means that 'é' becomes 'e' instead of '_' or 'e_'
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ident = "".join(c for c in ident if not unicodedata.combining(c))
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# TODO allow non-ascii characters in identifiers when using Python 3
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ident = _invalid_ident_char_re.sub('_', ident).lstrip('_')
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ident = _invalid_ident_start_re.sub(prefix, ident)
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if not ident:
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return ident
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if capitalize:
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# Just capitalize the first letter (do NOT lowercase other letters like str.title() does).
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ident = ident[0].capitalize() + ident[1:]
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# Prevent names that are illegal to assign to
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# iskeyword doesn't catch None/True/False in Python 2.x, but does in 3.x
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# (None is actually an error, Python 2.x doesn't make assigning to True or False an error,
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# but I think we don't want to allow users to do that)
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while iskeyword(ident) or ident in ['None', 'True', 'False']:
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ident = prefix + ident
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return ident
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_ends_in_digit_re = re.compile(r'\d$')
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def _add_suffix(ident_base, avoid=set(), next_suffix=1):
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"""
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Helper which appends a numerical suffix to ident_base, incrementing it until the result doesn't
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conflict with anything in the `avoid` set.
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"""
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if _ends_in_digit_re.search(ident_base):
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ident_base += "_"
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while True:
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ident = "%s%d" % (ident_base, next_suffix)
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if ident.upper() not in avoid:
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return ident
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next_suffix += 1
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def _maybe_add_suffix(ident, avoid):
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"""
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Returns the first of ident, ident2, ident3 etc. that's not in the `avoid` set.
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"""
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return ident if (ident.upper() not in avoid) else _add_suffix(ident, avoid, 2)
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def _uppercase(avoid):
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return {name.upper() for name in avoid}
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def pick_table_ident(ident, avoid=set()):
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"""
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Given a suggested identifier (which may be None), creates a sanitized table identifier,
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possibly with a numerical suffix that doesn't conflict with anything in the `avoid` set.
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"""
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avoid = _uppercase(avoid)
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ident = _sanitize_ident(ident, prefix="T", capitalize=True)
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return _maybe_add_suffix(ident, avoid) if ident else _add_suffix("Table", avoid, 1)
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def pick_col_ident(ident, avoid=set()):
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"""
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Given a suggested identifier (which may be None), creates a sanitized column identifier,
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possibly with a numerical suffix that doesn't conflict with anything in the `avoid` set.
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"""
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avoid = _uppercase(avoid)
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ident = _sanitize_ident(ident, prefix="c")
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return _maybe_add_suffix(ident, avoid) if ident else _gen_ident(avoid)
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def pick_col_ident_list(ident_list, avoid=set()):
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"""
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Given a list of suggested identifiers (which may be invalid), returns a list of valid sanitized
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unique identifiers, that don't conflict with anything in the `avoid` set or with each other.
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"""
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avoid = _uppercase(avoid)
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result = []
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for ident in ident_list:
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ident = pick_col_ident(ident, avoid=avoid)
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avoid.add(ident.upper())
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result.append(ident)
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return result
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def _gen_ident(avoid):
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"""
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Helper for pick_ident, which generates a valid identifier
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when pick_ident is called without a suggested identifier or default.
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It returns the first identifier that does not conflict with any elements of the avoid set.
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The identifier is a letter or combination of letters that follows a
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similar pattern to what excel uses for naming columns.
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i.e. A, B, ... Z, AA, AB, ... AZ, BA, etc
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"""
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avoid = _uppercase(avoid)
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for letter in _make_letters():
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if letter not in avoid:
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return letter
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def _make_letters():
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length = 1
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while True:
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for letters in itertools.product(ascii_uppercase, repeat=length):
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yield ''.join(letters)
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length +=1
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