A more flexible fix for custom tag constructors #279

ingydotnet · 2019-03-19T18:03:10Z

For #266 and #271. Replaces #273.

The yaml_loader class variable can be a list of loaders.
The YAMLObject helper class targets all the loader classes except SafeLoader.

Here's a test script that works. Uncomment the comments to support SafeLoader:

    #!/usr/bin/env python
    import yaml

    class Monster(yaml.YAMLObject):
        yaml_tag = u'!Monster'

        # yaml_loader = yaml.YAMLObject.yaml_loader
        # yaml_loader.append(yaml.SafeLoader)

        def __init__(self, name, hp, ac, attacks):
            self.name = name
            self.hp = hp
            self.ac = ac
            self.attacks = attacks
        def __repr__(self):
            return "%s(name=%r, hp=%r, ac=%r, attacks=%r)" % (
                self.__class__.__name__, self.name, self.hp, self.ac, self.attacks)

    input = """
    --- !Monster
    name: Cave spider
    hp: [2,6]    # 2d6
    ac: 16
    attacks: [BITE, HURT]
    """

    print(yaml.load(input))
    print(yaml.load(input, Loader=yaml.Loader))

    print(yaml.full_load(input))
    print(yaml.load(input, Loader=yaml.FullLoader))

    print(yaml.unsafe_load(input))
    print(yaml.load(input, Loader=yaml.UnsafeLoader))

    # print(yaml.safe_load(input))
    # print(yaml.load(input, Loader=yaml.SafeLoader))

Here is output:

$ PYTHONPATH=lib3 python3 test.py
test.py:27: YAMLLoadWarning: calling yaml.load() without Loader=... is deprecated, as the default Loader is unsafe. Please read https://msg.pyyaml.org/load for full details.
  print(yaml.load(input))
Monster(name='Cave spider', hp=[2, 6], ac=16, attacks=['BITE', 'HURT'])
Monster(name='Cave spider', hp=[2, 6], ac=16, attacks=['BITE', 'HURT'])
Monster(name='Cave spider', hp=[2, 6], ac=16, attacks=['BITE', 'HURT'])
Monster(name='Cave spider', hp=[2, 6], ac=16, attacks=['BITE', 'HURT'])
Monster(name='Cave spider', hp=[2, 6], ac=16, attacks=['BITE', 'HURT'])
Monster(name='Cave spider', hp=[2, 6], ac=16, attacks=['BITE', 'HURT'])

Works with Python 2 as well.

When someone writes a subclass of the YAMLObject class, the constructors will now be added to all 3 (non-safe) loaders. Furthermore, we support the class variable `yaml_loader` being a list, offering more control of which loaders are affected. To support safe_load in your custom class you could add this: yaml_loader = yaml.SafeLoader yaml_loader = yaml.YAMLObject.yaml_loader yaml_loader.append(yaml.SafeLoader)

kgutwin · 2019-03-19T18:44:35Z

I like this solution. Were you also planning to address the convenience methods issue as raised in #271?

Also, while this isn't really in the scope for this PR, I noticed during my review that the convenience methods scan(), parse(), compose() and compose_all() still reference Loader rather than FullLoader as their default Loader. For consistency, it may make sense to update those to behave similarly to load() and load_all().

ingydotnet · 2019-03-19T20:01:16Z

@kgutwin Thanks for your time.

I think #274 is meant to address the convenience methods. You should review and comment there.

perlpunk · 2019-03-19T20:08:03Z

This could actually work. The only thing it would break is cls.yaml_loader in from_yaml(). But since from_yaml() gets a loader instance, probably nobody would use the class attribute.
For the record, just add this to the script:

    @classmethod
    def from_yaml(cls, loader, node):

        # do something with cls.yaml_loader

        data = loader.construct_mapping(node)
        print(data['name'])
        a, b = map(int, data['hp'].split('d'))
        return cls(data['name'], [a, b], data['ac'], data['attacks'])

and change the input like this:

input = """
--- !Monster
name: Cave spider
#hp: [2,6]    # 2d6
hp: 2d6
ac: 16
attacks: [BITE, HURT]
"""

The only thing I'm not sure about is if people would want to have their objects added to three loaders.

I would not add SafeLoader. Things should only be added to SafeLoader explicitly.

perlpunk · 2019-03-19T20:13:38Z

For #266 and #271.

I think it does not address #271

perlpunk · 2019-03-19T20:28:13Z

To be really consistent, yaml.add_constructor should also add to three loaders.

kgutwin · 2019-03-19T23:38:05Z

The only thing I'm not sure about is if people would want to have their objects added to three loaders.

If my experience is anything of a "typical user", I'd say the vast majority of people don't care about the internal structure of PyYAML Loaders and would just like the module to work 😄 That's why I think this fix is a good strategy - it solves the broadest set of cases, and for users who want to be more fine-grained about their use of Loaders, it's easy for them to set the yaml_loader class attribute.

perlpunk · 2019-03-22T16:10:24Z

I created #287 which adds the same kind of logic to yaml.add_constructor

5.2: * Repair incompatibilities introduced with 5.1. The default Loader was changed, but several methods like add_constructor still used the old default yaml/pyyaml#279 -- A more flexible fix for custom tag constructors yaml/pyyaml#287 -- Change default loader for yaml.add_constructor yaml/pyyaml#305 -- Change default loader for add_implicit_resolver, add_path_resolver * Make FullLoader safer by removing python/object/apply from the default FullLoader yaml/pyyaml#347 -- Move constructor for object/apply to UnsafeConstructor * Fix bug introduced in 5.1 where quoting went wrong on systems with sys.maxunicode <= 0xffff yaml/pyyaml#276 -- Fix logic for quoting special characters * Other PRs: yaml/pyyaml#280 -- Update CHANGES for 5.1

https://github.com/yaml/pyyaml/blob/d0d660d035905d9c49fc0f8dafb579d2cc68c0c8/CHANGES#L7 5.3.1 (2020-03-18) * yaml/pyyaml#386 -- Prevents arbitrary code execution during python/object/new constructor 5.3 (2020-01-06) * yaml/pyyaml#290 -- Use `is` instead of equality for comparing with `None` * yaml/pyyaml#270 -- fix typos and stylistic nit * yaml/pyyaml#309 -- Fix up small typo * yaml/pyyaml#161 -- Fix handling of __slots__ * yaml/pyyaml#358 -- Allow calling add_multi_constructor with None * yaml/pyyaml#285 -- Add use of safe_load() function in README * yaml/pyyaml#351 -- Fix reader for Unicode code points over 0xFFFF * yaml/pyyaml#360 -- Enable certain unicode tests when maxunicode not > 0xffff * yaml/pyyaml#359 -- Use full_load in yaml-highlight example * yaml/pyyaml#244 -- Document that PyYAML is implemented with Cython * yaml/pyyaml#329 -- Fix for Python 3.10 * yaml/pyyaml#310 -- increase size of index, line, and column fields * yaml/pyyaml#260 -- remove some unused imports * yaml/pyyaml#163 -- Create timezone-aware datetimes when parsed as such * yaml/pyyaml#363 -- Add tests for timezone 5.2 (2019-12-02) ------------------ * Repair incompatibilities introduced with 5.1. The default Loader was changed, but several methods like add_constructor still used the old default yaml/pyyaml#279 -- A more flexible fix for custom tag constructors yaml/pyyaml#287 -- Change default loader for yaml.add_constructor yaml/pyyaml#305 -- Change default loader for add_implicit_resolver, add_path_resolver * Make FullLoader safer by removing python/object/apply from the default FullLoader yaml/pyyaml#347 -- Move constructor for object/apply to UnsafeConstructor * Fix bug introduced in 5.1 where quoting went wrong on systems with sys.maxunicode <= 0xffff yaml/pyyaml#276 -- Fix logic for quoting special characters * Other PRs: yaml/pyyaml#280 -- Update CHANGES for 5.1

- Update from 3.13 to 6.0 - Update of rootfile - Changelog 6.0 (2021-10-13) * yaml/pyyaml#327 -- Change README format to Markdown * yaml/pyyaml#483 -- Add a test for YAML 1.1 types * yaml/pyyaml#497 -- fix float resolver to ignore `.` and `._` * yaml/pyyaml#550 -- drop Python 2.7 * yaml/pyyaml#553 -- Fix spelling of “hexadecimal” * yaml/pyyaml#556 -- fix representation of Enum subclasses * yaml/pyyaml#557 -- fix libyaml extension compiler warnings * yaml/pyyaml#560 -- fix ResourceWarning on leaked file descriptors * yaml/pyyaml#561 -- always require `Loader` arg to `yaml.load()` * yaml/pyyaml#564 -- remove remaining direct distutils usage 5.4.1 (2021-01-20) * yaml/pyyaml#480 -- Fix stub compat with older pyyaml versions that may unwittingly load it 5.4 (2021-01-19) * yaml/pyyaml#407 -- Build modernization, remove distutils, fix metadata, build wheels, CI to GHA * yaml/pyyaml#472 -- Fix for CVE-2020-14343, moves arbitrary python tags to UnsafeLoader * yaml/pyyaml#441 -- Fix memory leak in implicit resolver setup * yaml/pyyaml#392 -- Fix py2 copy support for timezone objects * yaml/pyyaml#378 -- Fix compatibility with Jython 5.3.1 (2020-03-18) * yaml/pyyaml#386 -- Prevents arbitrary code execution during python/object/new constructor 5.3 (2020-01-06) * yaml/pyyaml#290 -- Use `is` instead of equality for comparing with `None` * yaml/pyyaml#270 -- Fix typos and stylistic nit * yaml/pyyaml#309 -- Fix up small typo * yaml/pyyaml#161 -- Fix handling of __slots__ * yaml/pyyaml#358 -- Allow calling add_multi_constructor with None * yaml/pyyaml#285 -- Add use of safe_load() function in README * yaml/pyyaml#351 -- Fix reader for Unicode code points over 0xFFFF * yaml/pyyaml#360 -- Enable certain unicode tests when maxunicode not > 0xffff * yaml/pyyaml#359 -- Use full_load in yaml-highlight example * yaml/pyyaml#244 -- Document that PyYAML is implemented with Cython * yaml/pyyaml#329 -- Fix for Python 3.10 * yaml/pyyaml#310 -- Increase size of index, line, and column fields * yaml/pyyaml#260 -- Remove some unused imports * yaml/pyyaml#163 -- Create timezone-aware datetimes when parsed as such * yaml/pyyaml#363 -- Add tests for timezone 5.2 (2019-12-02) * Repair incompatibilities introduced with 5.1. The default Loader was changed, but several methods like add_constructor still used the old default yaml/pyyaml#279 -- A more flexible fix for custom tag constructors yaml/pyyaml#287 -- Change default loader for yaml.add_constructor yaml/pyyaml#305 -- Change default loader for add_implicit_resolver, add_path_resolver * Make FullLoader safer by removing python/object/apply from the default FullLoader yaml/pyyaml#347 -- Move constructor for object/apply to UnsafeConstructor * Fix bug introduced in 5.1 where quoting went wrong on systems with sys.maxunicode <= 0xffff yaml/pyyaml#276 -- Fix logic for quoting special characters * Other PRs: yaml/pyyaml#280 -- Update CHANGES for 5.1 5.1.2 (2019-07-30) * Re-release of 5.1 with regenerated Cython sources to build properly for Python 3.8b2+ 5.1.1 (2019-06-05) * Re-release of 5.1 with regenerated Cython sources to build properly for Python 3.8b1 5.1 (2019-03-13) * yaml/pyyaml#35 -- Some modernization of the test running * yaml/pyyaml#42 -- Install tox in a virtualenv * yaml/pyyaml#45 -- Allow colon in a plain scalar in a flow context * yaml/pyyaml#48 -- Fix typos * yaml/pyyaml#55 -- Improve RepresenterError creation * yaml/pyyaml#59 -- Resolves #57, update readme issues link * yaml/pyyaml#60 -- Document and test Python 3.6 support * yaml/pyyaml#61 -- Use Travis CI built in pip cache support * yaml/pyyaml#62 -- Remove tox workaround for Travis CI * yaml/pyyaml#63 -- Adding support to Unicode characters over codepoint 0xffff * yaml/pyyaml#75 -- add 3.12 changelog * yaml/pyyaml#76 -- Fallback to Pure Python if Compilation fails * yaml/pyyaml#84 -- Drop unsupported Python 3.3 * yaml/pyyaml#102 -- Include license file in the generated wheel package * yaml/pyyaml#105 -- Removed Python 2.6 & 3.3 support * yaml/pyyaml#111 -- Remove commented out Psyco code * yaml/pyyaml#129 -- Remove call to `ord` in lib3 emitter code * yaml/pyyaml#149 -- Test on Python 3.7-dev * yaml/pyyaml#158 -- Support escaped slash in double quotes "\/" * yaml/pyyaml#175 -- Updated link to pypi in release announcement * yaml/pyyaml#181 -- Import Hashable from collections.abc * yaml/pyyaml#194 -- Reverting yaml/pyyaml#74 * yaml/pyyaml#195 -- Build libyaml on travis * yaml/pyyaml#196 -- Force cython when building sdist * yaml/pyyaml#254 -- Allow to turn off sorting keys in Dumper (2) * yaml/pyyaml#256 -- Make default_flow_style=False * yaml/pyyaml#257 -- Deprecate yaml.load and add FullLoader and UnsafeLoader classes * yaml/pyyaml#261 -- Skip certain unicode tests when maxunicode not > 0xffff * yaml/pyyaml#263 -- Windows Appveyor build Signed-off-by: Adolf Belka <adolf.belka@ipfire.org> --git a/config/rootfiles/packages/python3-yaml b/config/rootfiles/packages/python3-yaml x 0870a2346..bd4009a08 100644 * yaml/pyyaml#195 -- Build libyaml on travis * yaml/pyyaml#196 -- Force cython when building sdist * yaml/pyyaml#254 -- Allow to turn off sorting keys in Dumper (2) * yaml/pyyaml#256 -- Make default_flow_style=False * yaml/pyyaml#257 -- Deprecate yaml.load and add FullLoader and Uns oader classes * yaml/pyyaml#261 -- Skip certain unicode tests when maxunicode not xffff * yaml/pyyaml#263 -- Windows Appveyor build Signed-off-by: Adolf Belka <adolf.belka@ipfire.org> Reviewed-by: Peter Müller <peter.mueller@ipfire.org>

ingydotnet mentioned this pull request Mar 19, 2019

Change default loader for YAMLObject classes to FullLoader #273

Closed

perlpunk added this to PRs and Notes to Consider in 5.2 Release Mar 19, 2019

perlpunk mentioned this pull request Mar 22, 2019

Change default loader for yaml.add_constructor #287

Merged

perlpunk changed the base branch from master to release/5.2 March 31, 2019 14:19

perlpunk merged commit db91810 into release/5.2 Mar 31, 2019

perlpunk moved this from PRs and Notes to Consider to PyYAML release/5.2 branch in 5.2 Release Mar 31, 2019

mzagozen mentioned this pull request Apr 26, 2019

Pin PyYAML==3.13 and fix unit tests an2deg/pyraml-parser#37

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dthkao mentioned this pull request Sep 10, 2019

Incompatible changes in version 5.1 #265

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perlpunk deleted the ingydotnet/custom-constructor-fix branch December 2, 2019 22:53

asherf mentioned this pull request Apr 29, 2020

Upgrade PyYAML 5.1.2 to 5.3.1 pantsbuild/pants#9649

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Bump pyyaml from 3.13 to 5.4 mawy7/gra-asokwa-tincenter#5

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Bump pyyaml from 5.1.2 to 5.4 lwinterface/panini_microservice_template#133

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A more flexible fix for custom tag constructors #279

A more flexible fix for custom tag constructors #279

ingydotnet commented Mar 19, 2019

kgutwin commented Mar 19, 2019

ingydotnet commented Mar 19, 2019

perlpunk commented Mar 19, 2019

perlpunk commented Mar 19, 2019

perlpunk commented Mar 19, 2019

kgutwin commented Mar 19, 2019

perlpunk commented Mar 22, 2019

A more flexible fix for custom tag constructors #279

A more flexible fix for custom tag constructors #279

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ingydotnet commented Mar 19, 2019

kgutwin commented Mar 19, 2019

ingydotnet commented Mar 19, 2019

perlpunk commented Mar 19, 2019

perlpunk commented Mar 19, 2019

perlpunk commented Mar 19, 2019

kgutwin commented Mar 19, 2019

perlpunk commented Mar 22, 2019