Fable 5, not compatible with Fable 4 plugins

[MangelMaxime]

Description

When releasing Fable 5.0.0-alpha.1, the tests didn't capture the fact that upgrading Fable version would make Fable 4 plugins not supported.

This happened because when running the tests, we don't upgrade Fable internal version so it was still checking against version 4.24.0

Solutions

1. We ask Fable plugins to upgrade their FableMinimumVersion to 5.0.

   Pro we don't need to do anything on Fable side.

   Cons this will create a new shift in Fable ecosystem, because then Feliz will need to create a new major version. Which could cause a cascade of upgrade needed for others packages that depends on it.

   The problem is that package authors are not as active as before, so this cascade change can take some time.

2. We adapt Fable logic to allows plugins requesting FableMinimumVersion = "4.0" to works with Fable 5.

   Pro Fable compiler plugins and others NuGet packages depending on them will need to do nothing. This seems also more aligned with the name of the property FableMinimumVersion. It says minimum version and not major version.

   Cons we will start to make custom logic allowing to support different span of Fable compiler plugins. This would allows us to say as long as Fable.AST stay stable we can support the same plugin for Fable 4, 5, 6, etc.

   This question also if we should not have used the version of Fable.AST assembly (I think .NET as version info in the assembly) instead of an arbitrary FableMinimumVersion property.

What do you think @ncave @dbrattli ?

[ncave]

@MangelMaxime IMO staying with FableMinimumVersion = "4.0" makes sense, since Fable AST hasn't changed (so # 2 above).

[MangelMaxime]

I forgot to mention it, but I am also in favour of # 2.

[nojaf]

5.0.0-alpha.1 is a different notation to how the 4.0.0-theta-018 was used in the past.
Regex over at

Fable/src/Fable.Transforms/Global/Compiler.fs

Lines 102 to 124 in 04f23a0

	let private expectedVersionMatchesActual (expected: string) (actual: string) =
	try
	let r = System.Text.RegularExpressions.Regex(@"^(\d+)\.(\d+)(?:\.(\d+))?")
	let parse v =
	let m = r.Match(v)
	int m.Groups[1].Value,
	int m.Groups[2].Value,
	if m.Groups[3].Success then
	int m.Groups[3].Value
	else
	0
	let actualMajor, actualMinor, actualPatch = parse actual
	let expectedMajor, expectedMinor, expectedPatch = parse expected
	// Fail also if actual major is bigger than expected major version
	actualMajor = expectedMajor
	&& (actualMinor > expectedMinor
	|| (actualMinor = expectedMinor && actualPatch >= expectedPatch))
	with _ ->
	false

probably no longer matches.

[ncave]

@nojaf

probably no longer matches.

No, that Regex just matches the version parts, should be ok, see #3963.