WebAssembly
Weak Imports
Should we model weak imports as a Bindings-layer feature?
It's a feature that can be expressed in terms of bindings, it affects how modules are wired together, and it's a weaker constraint on the environment than wasm imports (which state "give me this or I will fail to instantiate").
At a first stab, we can describe this feature with no new wasm-core functionality, by for example adding a pair of bindings, one to wrap the imported object (with either the object if present, or something that traps if not), and a boolean global to check if the import succeeded or not.
Maybe not for MVP which makes the timing awkward? Or maybe it's compelling enough to add.
This was mentioned in this morning's WASI meeting, @sunfishcode more thoughts? Previous discussions: https://github.com/WebAssembly/WASI/issues/36 , https://github.com/WebAssembly/design/issues/1281
IMO, you do not need a specific 'weak import' concept if you use 'web interoperability bindings'. In the case where an actual import is not provided, you can provide a stub 'implementation' via the binding lambda.
On Thu, Jul 18, 2019 at 9:34 AM Jacob Gravelle [email protected] wrote:
Should we model weak imports as a Bindings-layer feature?
It's a feature that can be expressed in terms of bindings, it affects how modules are wired together, and it's a weaker constraint on the environment than wasm imports (which state "give me this or I will fail to instantiate").
At a first stab, we can describe this feature with no new wasm-core functionality, by for example adding a pair of bindings, one to wrap the imported object (with either the object if present, or something that traps if not), and a boolean global to check if the import succeeded or not.
Maybe not for MVP which makes the timing awkward? Or maybe it's compelling enough to add.
This was mentioned in this morning's WASI meeting, @sunfishcode https://github.com/sunfishcode more thoughts? Previous discussions: WebAssembly/WASI#36 https://github.com/WebAssembly/WASI/issues/36 , WebAssembly/design#1281 https://github.com/WebAssembly/design/issues/1281
— You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub https://github.com/WebAssembly/webidl-bindings/issues/48?email_source=notifications&email_token=AAQAXUADYIEEMAWXMFMB57TQACLPTA5CNFSM4IE5POR2YY3PNVWWK3TUL52HS4DFUVEXG43VMWVGG33NNVSW45C7NFSM4HABVIGA, or mute the thread https://github.com/notifications/unsubscribe-auth/AAQAXUHD5V57VA6NUBTEW4DQACLPTANCNFSM4IE5PORQ .
-- Francis McCabe SWE
In the case where an actual import is not provided, you can provide a stub 'implementation' via the binding lambda.
That's the core idea I think. Something like
(@bindings weak-import "external" "global"
(if-present Integer-as-i32) ;; import binding
(if-absent (i32.const 0)) ;; default value
)