Deprecate execution of "uncomponentizable" WAGI modules

[lann]

⚠️ This deprecation process is complete with Spin 3.0. If you've come here from a Spin error message, the following may still be relevant to you:

My module has been deprecated! What can I do?

This deprecation most likely impacts you only if:

• you are using the WAGI executor, and
• you are not using wit-bindgen, and
• you are using a module compiled with a version of clang < 15.0.7, indicating likely usage of wasi-sdk <19

If you have access to the relevant source code, updating wasi-sdk to at least version 19 can avoid this deprecation.

The Problem

Wasm modules compiled with old versions of wasi-sdk <18 have a bug that makes them incompatible with the wasi-preview1-adapter, which in turn means we cannot convert these modules into components. Maintaining support for executing these uncomponentizable modules represents a significant ongoing maintenance burden, but - as far as we can tell - has been used by very few users, especially recently.

Deprecation Details

We can heuristically detect these modules:

• If a module exports cabi_realloc, it should be safe to componentize, regardless of the version of clang / wasi-sdk
• If a module has a producers section indicating that it was compiled with clang < 15.0.7, it was probably compiled with a buggy version of wasi-sdk

Implementation of this deprecation would include:

• Immediately using the above algorithm to implement a deprecation warning in Spin 2.6 (Add deprecation warning for uncomponentizable modules #2571)
• Actually drop support for these modules when Spin Factors #2519 is merged, possibly motivating a major version bump to Spin 3.0

[michelleN]

@lann For 3.0 - is the action item here mainly documentation at this point or are there other action items?

[michelleN]

Thinking about it more, seems like we'll need an error on spin up as now it's a deprecation notice.

[michelleN]

We'll also want to remove any templates for WAGI apps and templates referencing WAGI including:

• http-php
• http-grain
• http-zig

[itowlson]

The Grain one at least looks like it's been recently fixed to enable componentisation. This doesn't affect all WAGI apps, only ones that can't be componentised (see criteria above) - does the Grain one still fall foul of that?