Verify TASTy versions before releases

We need to verify before releases that TASTy is set to a correct version.

Here is a very simplistic approach that could be automated to ensure that we don’t accidentally release experimental TASTy in a stable release, or stable TASTy in a Nightly release:

(mStable refers to the TastyFormat.MinorVersion of the most recent stable Scala release)

if MajorBump:
  raise "are you really sure?"
else if Nightly or (MinorBump and RC or Milestone):
  assert TastyFormat.ExperimentalVersion > 0
  assert TastyFormat.MinorVersion > mStable
else: # release is final
  assert ExperimentalVersion == 0
  if PatchBump:
    assert TastyFormat.MinorVersion == mStable
  else if MinorBump:
    assert TastyFormat.MinorVersion == mStable + 1

with the proposal above, the only clear weak link is that TastyFormat.MinorVersion should be increased in a nightly release before releasing the next Minor, but I propose that this is difficult to miss as it should be clear that merging a needs-minor-release PR needs a TASTy version bump

A next step would be to automate the weak-link I described above.

A simple way could be automating the creation of an issue whenever a needs-minor-release PR is merged, otherwise it will probably be too complex to analyse automatically ( requires analysing TreePickler, TastyFormat, API additions, Code synthesis changes, more)

[bishabosha]

ok here is an updated diagram with past and future - hopefully this makes a coherent model:

        Stable             Beta             Nightly

━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━
   ┌───────────────┐                   ┌───────────────┐
   │ T: 28.0-0     │                   │ T: 28.1-1     │
   │ S: 3.0.0      │                   │ S: 3.0.1-NI-a │
   └───────────────┘ ┌───────────────┐ └───────────────┘
           │         │ T: 28.0-0     │         │
           │         │ S: 3.0.1-RC1  │         ▼
           │         └───────────────┘ ┌───────────────┐
           │                 │         │ T: 28.1-1     │
           │                 ▼         │ S: 3.0.2-NI-b │
           │         ┌───────────────┐ └───────────────┘
           │         │ T: 28.0-0     │         │
           ▼         │ S: 3.0.1-RC2  │         │
   ┌───────────────┐ └───────────────┘         │
   │ T: 28.0-0     │         │                 │
   │ S: 3.0.1      │         ▼                 │
   └───────────────┘ ┌───────────────┐         │
           │         │ T: 28.0-0     │         │
           │         │ S: 3.0.2-RC1  │         ▼
           │         └───────────────┘ ┌───────────────┐
           │                 │         │ T: 28.2-1     │
           │                 ▼         │ S: 3.1.0-NI-c │
           │         ┌───────────────┐ └───────────────┘
           │         │ T: 28.0-0     │         │
           ▼         │ S: 3.0.2-RC2  │         │
   ┌───────────────┐ └───────────────┘         │
   │ T: 28.0-0     │         │                 │
   │ S: 3.0.2      │         ▼                 │
   └───────────────┘ ┌───────────────┐         │
           │         │ T: 28.2-1     │         │
           │         │ S: 3.1.0-RC1  │         ▼
           │         └───────────────┘ ┌───────────────┐
           │                 │         │ T: 28.2-1     │
           │                 │         │ S: 3.1.1-NI-d │
           │      ┏━━━━━━━━┓ │         └───────────────┘
           │      ┃  past  ┃ │                 │
▣━━━━━━━━━━╋━━━━━━┻━━━━━━━━┻━╋━┳━━━━━━━━┳━━━━━━╋━━━━━━━━━▣
           │                 │ ┃ future ┃      │
           │                 │ ┗━━━━━━━━┛      │
           │                 ▼                 │
           │         ┌───────────────┐         │
           │         │ T: 28.1-2     │         │
           ▼         │ S: 3.1.0-RC2  │         │
   ┌───────────────┐ └───────────────┘         │
   │ T: 28.1-0     │         │                 │
   │ S: 3.1.0      │         ▼                 │
   └───────────────┘ ┌───────────────┐         │
           │         │ T: 28.1-0     │         │
           │         │ S: 3.1.1-RC1  │         ▼
           │         └───────────────┘ ┌───────────────┐
           │                 │         │ T: 28.3-1     │
           ▼                 │         │ S: 3.2.0-NI-e │
   ┌───────────────┐         │         └───────────────┘
   │ T: 28.1-0     │         │                 │
   │ S: 3.1.1      │         ▼                 │
   └───────────────┘ ┌───────────────┐         │
           │         │ T: 28.2-2     │         │
           │         │ S: 3.2.0-RC1  │         ▼
           │         └───────────────┘ ┌───────────────┐
           │                 │         │ T: 28.3-1     │
           │                 ▼         │ S: 3.2.1-NI-f │
           │         ┌───────────────┐ └───────────────┘
           │         │ T: 28.2-2     │
           ▼         │ S: 3.2.0-RC2  │
   ┌───────────────┐ └───────────────┘
   │ T: 28.2-0     │
   │ S: 3.2.0      │
   └───────────────┘

[bishabosha]

So with the rule of RCs having experimental versions then this is what the future of releases could look like - I have included examples of both a patch release and a minor release.

each row represents the releases made each 6 weeks

Edit: removed diagram - see https://github.com/lampepfl/dotty/issues/13447#issuecomment-912447107 for updated diagram