Revisit the way packs work - always unpack them

[nicolas-grekas]

Packs create issues like symfony/orm-pack#25

For sure, we don't want to maintain versions of packs each time a dependent is bumped.
The current solution is like: use packs until it breaks for you, then unpack.

Instead, I'd like to propose the following:

• keep using * as the version constraint for dependents in packs,
• auto-unpack when installing a pack,
• auto-replace the * by the current version - compute this "current version" by borrowing what composer does when running compose require without a version constraint (when the package is already found in the main composer.json, skip this),
• additionally, also unpack require-dev,
• (skip "conflict" and/or "replace", that's too much work, better consider them unsupported in packs, until one contributes the logic at least?).

Related to symfony/orm-pack#26, #370, #371, #563

[stof]

For sure, we don't want to maintain versions of packs each time a dependent is bumped.

Why wouldn't we want to do that ? AFAIK, we don't have lots of packs involving non-Symfony packages (Symfony packages being covered by the special Symfony constraint of Flex).

Unpacking automatically in the require command when Flex is overriding it will still not prevent people from having such package in their requirement for another reason. If we keep an * requirement there, we would have to explicitly document that our pack packages are not following semver at all and are not covered by the Symfony BC promise.

[nicolas-grekas]

Because there's zero value in doing so. We need to simplify our processes. I would dedicate zero minutes of my OSS time to maintaining this. And I'm sure that's the same for everyone.

semver/BC policy is about code, not about dependencies. That's a common misunderstanding.

What issues do you see in that proposal? Combined with flex (packs are a flex-only thing), resolving the * when unpacking has no drawbacks to me.

[stof]

@nicolas-grekas semver is about the public API of your package, which might involve some APIs defined in dependencies (if you return one of their objects for instance). For a pack, the only API it has are the transitive dependencies, as that's what the pack is about.

[stof]

packs are a flex-only thing

They are not. they are registered on Packagist as normal packages.

[nicolas-grekas]

There is no API in a pack. This interpretation you give is way too broad.

packs are a flex-only thing

Yes they are: "type": "symfony-pack". If one installs a pack and doesn't use flex, they're on their own.

[nicolas-grekas]

In #651, I made * be turned into regular constraints when unpacking.
In #652, I'm proposing to unpack recursively.

About unpack-by-default, there is a drawback: it will make uninstalling them impossible.
We need to decide if this a major flaw and if there is a way around before going this route.
An alternative option might be to make this configurable, via e.g. extra.auto-unpack or similar.
WDYT on this point?

About skipping conflicts, that might be unneeded actually: when packs are installed, the conflicts are taken into account. Now that #651 locks the major version of installed packages when unpacking, this kinda freezes the resolved conflicts. Of course, it's always possible that removing the conflicts will yield a different solution after unpacking, but the window becomes quite narrow. Maybe narrow enough to close #371 and save us from spending time on this.

For "replace", we should unpack them, see #653

Unpacking require-dev should be done separately, see #654