[WASM] CR transition for WebAssembly JavaScript Interface

[binji]

Document title, URIs, estimated publication date

target: https://www.w3.org/TR/2019/CR-wasm-js-api-1-20190516/
source: http://webassembly.github.io/spec/js-api/
to be published with: to be published with: Core and WebAPI

Abstract

This document provides an explicit JavaScript API for interacting with WebAssembly.

Part of a collection of related documents: the Core WebAssembly Specification, the WebAssembly JS Interface, and the WebAssembly Web API.

Status

Standard bikeshed SOTD plus advice that the following issue may change implementations:
[[
#985. [js-api] Review object caching (Mar 14, 2019)
postMessage re-uses existing objects so as not to not grow memory
]]

Decision to request transition

https://github.com/WebAssembly/meetings/blob/master/2019/WG-02-13.md#--request-that-we-move-forward-with-a-candidate-recommendation-cr

Changes

• validate(bytes) makes a copy of the bytes before validating.
• asynchronous compilation is done in parallel with constructing the module object.
• Instantiating a module is split into steps, so the logic can be reused for synchronous and asynchronous instantiation: read the imports, create an instance object, and instantiate the core of a WebAssembly module.
• Separate create a memory buffer from create a memory object, to allow reuse in reset the Memory buffer.
• "initial" in Memory descriptor is required.
• maximum < initial throws a RangeError.
• define Memory.buffer getter.
• "initial" in Table descriptor is required.
• Define ValueType enum.
• Separate run a host function from create a host function
• Added List of implementation-defined limits
• Added Security and Privacy section

Requirements satisfied

N/A

Dependencies met

Some changes to WebAssembly core.

Wide Review

Reviewed with WebAssembly core specification, see list in #119.

Issues Addressed

Issues are addressed on http://github.com/WebAssembly/spec. See, for example, the following issues related to this specification:

• [js-api] "Creating a host function" requires a functype parameter WebAssembly/spec#768
• [js-api] Allow creating i64 globals WebAssembly/spec#827
• [jsapi] Should MemoryDescriptor["initial"] be required? WebAssembly/spec#838
• [jsapi] Memory#buffer has no definition WebAssembly/spec#840
• [jsapi] "reset the Memory buffer" doesn't set [[ArrayBufferDetachKey]] on the new ArrayBuffer WebAssembly/spec#855
• Spec for Memory object's constructor does not check maximum >= initial WebAssembly/spec#876
• Appropriate error for exceeding an implementation limit for table or memory size WebAssembly/spec#879
• [jsapi] Inconsistency with custom section decoding  WebAssembly/spec#914
• [jsapi] inconsistent utf-8 decoding WebAssembly/spec#915
• [jsapi] limit tests optimization WebAssembly/spec#972

Open issues:
#810. js api: improve definition of error objects (editorial)
#741. [js-api] Allow optional asynchronous steps after instantiation? (awaiting close by commenter)

Formal Objections

None.

Implementation

See results for 4 implementations at https://wpt.fyi/results/wasm/jsapi.

• *.any.js failures are an infrastructure bug.
• one grow.any.* failure includes a test for a future feature which is not yet enabled by default.

Patent disclosures

https://www.w3.org/2004/01/pp-impl/101196/status#current-disclosures

[binji]

@ericprud

[swickr]

Transition approved.

Looking forward to the resolution of #1026 and the similar one for Object.

[plehegar]

Published
https://www.w3.org/TR/2019/CR-wasm-js-api-1-20190718/