Isolate caller-supplied metadata with deepcopy - #65
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Use two separate deep copies in Parameters.__init__: 1. __full_metadata: pristine copy, never mutated by the instance. Used by create_subset() to build child Parameters instances that need the original unresolved metadata (dimension names in bounded 'maximum' fields, original dimension sizes, etc.). 2. _working_metadata: separate working copy that self.metadata, self.__dimensions, and all Parameter instances are free to mutate (bounded resolution, dimension size changes, etc.). This supersedes the need for shallow copies in Parameter.__init__ and Dimension.__init__ since the caller's dict is never passed into the internal machinery. The approach also prevents create_subset() from crashing due to mutated __full_metadata, which would happen if __full_metadata and self.metadata shared sub-dicts. Addresses the same root cause as PR #64 (caller-supplied metadata being mutated across Parameters instances) but at a higher level, providing stronger guarantees.
This was referenced Aug 17, 2026
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Summary
Prevents caller-supplied metadata from being mutated by
Parametersinstances. Related to #64.Problem
Parameters.__init__previously shared sub-dicts betweenself.__full_metadataandself.metadata. When bounded parameter resolution or dimension size changes mutatedself.metadata, those changes leaked into__full_metadata. This causedcreate_subset()to pass already-resolved metadata (numericmaximuminstead of dimension name) to childParametersinstances, crashing on bounded parameteradd().The same root cause also affected callers who reuse a single
MetaData().metadatadict across multipleParametersinstances (e.g. pywatershed'sDomainSubsettests).Fix
Use two separate
deepcopycalls inParameters.__init__:__full_metadata— pristine copy, never mutated by the instance. Passed tocreate_subset()for building childParametersinstances._working_metadata— separate working copy thatself.metadata,self.__dimensions, and allParameterinstances are free to mutate (bounded resolution, dimension size changes, etc.).Since the caller's dict is never passed into the internal machinery, shallow copies in leaf classes (
Parameter.__init__,Dimension.__init__) are unnecessary — though harmless if also applied.Testing
All 302 tests pass locally (Python 3.13).