Introduce ModelVarContext as a generalisation of ModelLookup and ModelFindVariables
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Occurrences of `ModelFindVariables` and `ModelLookup` in the `InLockstep` class are replaced by the newly exposed `ModelVarContext`. A `ModelFindVariables` can be recovered from a `ModelVarContext` using the new `findVars` functions. A `ModelLookup` can be recovered from a `ModelVarContext` using the new `lookupVars` function. Since these functions can be recovered from `ModelVarContext`, existing tests are guaranteed to be adaptable to the new `InLockstep` API. Motivation: previously in the `InLockstep` class, member functions would be passed a `ModelFindVariables` or a `ModelLookup`, but never both. In practice this turned out to be too restrictive, because one might want access to both in the same function, see IntersectMBO/lsm-tree#431. For example, `arbitraryWithVars` was previously only passed a `ModelFindVariables`, but without a `ModelLookup` one can not filter these variables based on the (modelled) outcome of the corresponding actions. The use case for #431 in particular was to filter variables that reference stateful handles (e.g., file handles) for handles that are open. Because of this filtering, one can skew the action distribution to generate more actions on open handles. It is often more interesting to test actions on open handles than it is to test actions on closed handles, which will presumably always return the same error.
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dcoutts
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Nov 5, 2024
| `findVars` functions. A `ModelLookup` can be recovered from a | ||
| `ModelVarContext` using the new `lookupVars` function. Since these functions | ||
| can be recovered from `ModelVarContext`, existing tests are guaranteed to be | ||
| adaptable to the new `InLockstep` API. |
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Might be nice to give an example of what you need to change?
arbitraryWithVars lookupVars = ...
(lookupVars ...)
becomes
arbitraryWithVars vctx = ...
(lookupVars vctx ...)
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Occurrences of
ModelFindVariablesandModelLookupin theInLockstepclass are replaced by the newly exposedModelVarContext. AModelFindVariablescan be recovered from aModelVarContextusing the newfindVarsfunctions. AModelLookupcan be recovered from aModelVarContextusing the newlookupVarsfunction. Since these functions can be recovered fromModelVarContext, existing tests are guaranteed to be adaptable to the newInLockstepAPI.Motivation: previously in the
InLockstepclass, member functions would be passed aModelFindVariablesor aModelLookup, but never both. In practice this turned out to be too restrictive, because one might want access to both in the same function, see IntersectMBO/lsm-tree#431. For example,arbitraryWithVarswas previously only passed aModelFindVariables, but without aModelLookupone can not filter these variables based on the (modelled) outcome of the corresponding actions. The use case for #431 in particular was to filter variables that reference stateful handles (e.g., file handles) for handles that are open. Because of this filtering, one can skew the action distribution to generate more actions on open handles. It is often more interesting to test actions on open handles than it is to test actions on closed handles, which will presumably always return the same error.