65 lines
2.3 KiB
Python
65 lines
2.3 KiB
Python
"""Reading a typed value out of the query string, without a 500.
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WHY THIS EXISTS
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List endpoints filtered like this:
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if type_id := request.args.get('typeid'):
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query = query.filter(Machine.machinetypeid == int(type_id))
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`int('abc')` raises, nothing catches it, and the caller gets
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500 INTERNAL_ERROR with a traceback in the log. A wrong query argument is the
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caller's mistake and deserves a 400 saying which argument; a 500 says the server
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is broken and sends whoever is reading the log looking for a fault that is not
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there. The feature test run found the same shape in six places across five
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plugins, which makes it a property of how list routes are written rather than of
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any one route.
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The helpers raise QueryArgError. Routes turn it into a 400 - or, more usually,
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nothing does anything at all, because the app-level handler in
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shopdb/__init__.py answers it. That is the point: a route should not have to
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remember.
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Deliberately NOT the same policy as get_pagination_params, which falls back to
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a default for a bad page number. A nonsense page is harmless and the caller
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still wants their list; a nonsense FILTER is not, because silently ignoring it
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returns rows the caller believes they excluded.
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"""
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from flask import request
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class QueryArgError(ValueError):
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"""A query argument was present but not of the type the route needs."""
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def __init__(self, name, value, expected='a whole number'):
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self.name = name
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self.value = value
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super().__init__('%s must be %s (got %r)' % (name, expected, value))
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def intarg(name, default=None, request_obj=None):
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"""Read an integer query argument.
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Absent or empty -> default. Present but not an integer -> QueryArgError,
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which the app answers as a 400 naming the argument.
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"""
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source = request_obj if request_obj is not None else request
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raw = source.args.get(name)
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if raw is None or raw == '':
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return default
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try:
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return int(raw)
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except (TypeError, ValueError):
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raise QueryArgError(name, raw)
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def intargs(*names, request_obj=None):
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"""Read several integer arguments at once; returns a dict of those present."""
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found = {}
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for name in names:
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value = intarg(name, request_obj=request_obj)
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if value is not None:
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found[name] = value
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return found
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