Closed azriel91 closed 8 months ago
Considering the value of this.
With it | Without it |
---|---|
Runtime error on mismatched types | Compilation error on mismatched types |
Need to define extra enum | Don't need to define extra enum |
Don't need to specify params spec for "used what was set last time" for mapping functions -- always set in cmd ctx | May forget specifying "used what was set last time" for mapping functions, and hit runtime error |
Define an enum to name the function keys:
enum MappingFunctions {
BucketNameFromBucketState,
IamPolicyArnFromIamPolicyState,
}
Define the mappings:
let mapping_functions = {
let mut mapping_functions = MappingFunctions::new();
mapping_functions.insert(BucketNameFromBucketState, S3BucketState::bucket_name);
// ..
mapping_functions
};
Note:
If we want to have a compilation error here, the MappingFunctions::insert
function needs to have a type parameter that tells it the Item > Params > Field
that the mapping function is for.
However, developers use #[derive(Params)]
to derive the <ItemParams>FieldWiseSpec
, and requiring them to specify something like the following is arduous:
MappingFunction::insert<FromType, ToType>(BucketNameFromBucketState, S3BucketState::bucket_name)
Pass MappingFunctions
to CmdCtxBuilder
, for each code instantiation (may be just one):
cmd_ctx_builder.with_mapping_functions(mapping_functions);
Not have to call .with_item_params::<TheItem>(..)
in subsequent calls.
MappingFunctions
map will have magic logic to store the function argument types and return type.Define the item params spec:
// First execution
let s3_object_params_spec = S3ObjectParams::<WebApp>::field_wise_spec()
.with_file_path(web_app_path_local)
.with_object_key(object_key)
.with_bucket_name_from_map(S3BucketState::bucket_name)
.build();
// Subsequent executions
let s3_object_params_spec = S3ObjectParams::<WebApp>::field_wise_spec()
.with_bucket_name_from_map(S3BucketState::bucket_name)
.build();
Pass the item params spec to CmdCtxBuilder
, for every separate code instantiation:
cmd_ctx_builder
.with_item_params::<S3ObjectItem<WebApp>>(
item_id!("s3_object"),
s3_object_params_spec,
)
This is somewhat of an inconvenience, because if this isn't done, the user / developer will have a runtime error, which looks like this:
peace_rt_model::params_specs_mismatch
× Item params specs do not match with the items in the flow.
help: The following items either have not had a params spec provided previously,
or had contained a mapping function, which cannot be loaded from disk.
So the params spec needs to be provided to the command context for:
* s3_object
When the closure passed to with_*_from_map
doesn't have the argument type specified, or mismatches, the compilation error is still unclear. https://github.com/rust-lang/rust/pull/119888 will allow us to return a useful compilation error.
No runtime error, because it will be caught at compile time.
CmdCtx
is missing which item spec for which field, should be made clear.
Enables the developer to not have to pass in params specs for items that had mapping functions.
Currently
ParamsSpec
and related types --ParamsSpecFieldless
,ValueSpec
,FieldWiseSpec
(generated by proc macro) -- holdMappingFn
s within their type.This forces users to respecify the params specs with mapping functions in subsequent
CmdCtx::builder_*
instantiation.This change is to:
Map<MappingFnK, Box<dyn MappingFn>>
, and pass that toCmdCtx::builder_*
.ParamsSpec
and related types will hold theMappingFnK
.MappingFnK
, an all-unit-variant enum with sensible names to identify the mapping function.