Strange effect when using pre-releases

[goto40]

When I adopt the manual to use pre-releases with v0.27.0 (thanks for that feature! :-) ):

[tool.bumpversion.parts.pre_l]
values = ["dev", "rc", "final"]
optional_value = "final"

but I just want "dev" to be present (no "rc", "final" and no optional_value)

[tool.bumpversion.parts.pre_l]
values = ["dev"]

I get an unexpected behavior (at least unexpected to me).

Instead of

$ bump-my-version show-bump
0.1.0 ── bump ─┬─ major ─ 1.0.0-dev0
               ├─ minor ─ 0.2.0-dev0
               ├─ patch ─ 0.1.1-dev0
               ├─ pre_l ─ invalid: The part has already the maximum value among ['dev', 'rc', 'final'] and cannot be bumped.
...

I then get

$ bump-my-version show-bump
0.1.0 ── bump ─┬─ major ─ 1.0.0
               ├─ minor ─ 0.2.0
               ├─ patch ─ 0.1.1
...

Is this intentional?

[coordt]

This is the expected behavior.

Here is some background

1. There is a difference between the values of all the parts and how they are serialized into a version. In the example in the docs, version 0.1.0 could also be serialized as 0.1.0-final0. The pre_l value final is optional as is the pre_n value of 0, and therefore means they doesn't have to be in the serialized version.
2. There is always an optional value. The first item in a list of values is the optional value, unless you indicate otherwise. In your alteration for pre_l and setting it to ["dev"], you have made dev optional. You have also made it the only allowed value.
3. Bump-my-version tries to selected the serialization method that requires the fewest components. The docs contain an explanation of how it selects a a serialization value.

If what you want is a releasing strategy that looks something like:

• 1.0.0-dev0
• 1.0.0-dev1
• 1.0.1

You would change the configuration of the pre_l component to only contain ["dev", "final"]

Was I able to answer your question?

[goto40]

Thank you very much for your quick reply! I need to take time to discuss your answer. I will reply next 10 days.

[goto40]

I was missing the fact that there is always one optional part. Thank you!