google/python-fire

Only plain literals should be parsed

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#97 opened on Oct 12, 2017

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Description

@dbieber correctly pointed out in #95 that there is a more general problem with the parsing code. This is a follow up issue to that issue which only dealt with the most common case of a single argument.

Here are some cases demonstrating

$ python3 -c "import fire.parser as p; v = p.DefaultParseValue('[1+1]'); print(type(v), v)"
<class 'list'> [2]
$ python3 -c "import fire.parser as p; v = p.DefaultParseValue('{key: 1+1}'); print(type(v), v)"
<class 'dict'> {'key': 2}

Some options are:

  1. Accept the existing behaviour.
  2. Always parse the whole argument as a string by doing raise ValueError in ``fire.parser._LiteralEval`
  3. Parse only the sub expressions as strings

For 2. and 3. I think these would be the valid types from the ast module.

  • Str
  • Name (converted to Str)
  • Num
  • List
  • Tuple
  • Dict
  • Set
  • UnaryOp

Contributor guide

Research direction
Inspect the DefaultParseValue function in fire/parser.py and modify LiteralEval to only allow specific AST node types (Str, Name, Num, List, Tuple, Dict, Set, UnaryOp) and raise ValueError for others.
Tech stack
python
Domain
cli
Issue type
Bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
2
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-3 hours
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
Python
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
70