Candidate Breaking Changes for 1.0

Candidate Breaking Changes for 1.0

This is a list of candidate breaking changes for 1.0. We will not necessarily go through with all of them! We're building a master list here so we can prioritize and decide which changes are worth it and which ones aren't worth the disruption.

High priority

• Replace non-usize size/index arguments with usize
• Drop the type argument from JsFunction
• Rename cx.global() to cx.global_object() and add cx.global::<JsFunction>("Array")

Rejected

• Align argument_opt() signature with argument() signature <== rejected: better forward-looking approach is Serde arg parsing
• Eliminate panics based on throwing state by having (nearly) all APIs return a Result
• Eliminate the Context trait and make it just a struct, passing Arguments as a second parameter to Neon functions
• Rename downcast_or_throw() <== let's try to avoid needing to do this, thanks to implicit downcasting in more contexts
• Keep cx.global() as-is and add cx.get::<JsFunction>("Array")? <== rejected: "context" suggests getting from local context, i.e. this
• Collapse all Context types except ModuleContext and FunctionContext <== rejected: we'll try to make new back-compat frontends for everything when we create the Env struct post-1.0

Done

• Add a private field to Throw so that it can't be constructed by users
• New Borrow API
• Create functions from closures
• Make Object::get() return generic type to eliminate need for casts
• Make JsFunction::call() return generic type to eliminate need for casts
• Remove JsResultExt; it's redundant with ResultExt
• No default backend