231 lines
10 KiB
Markdown
231 lines
10 KiB
Markdown
<!--
|
|
tagline: Versions explained.
|
|
-->
|
|
|
|
# Versions and constraints
|
|
|
|
## Composer Versions vs VCS Versions
|
|
|
|
Because Composer is heavily geared toward utilizing version control systems
|
|
like git, the term "version" can be a little ambiguous. In the sense of a
|
|
version control system, a "version" is a specific set of files that contain
|
|
specific data. In git terminology, this is a "ref", or a specific commit,
|
|
which may be represented by a branch HEAD or a tag. When you check out that
|
|
version in your VCS -- for example, tag `v1.1` or commit `e35fa0d` --, you're
|
|
asking for a single, known set of files, and you always get the same files back.
|
|
|
|
In Composer, what's often referred to casually as a version -- that is,
|
|
the string that follows the package name in a require line (e.g., `~1.1` or
|
|
`1.2.*`) -- is actually more specifically a version constraint. Composer
|
|
uses version constraints to figure out which refs in a VCS it should be
|
|
checking out (or simply to verify that a given library is acceptable in
|
|
the case of a statically-maintained library with a `version` specification
|
|
in `composer.json`).
|
|
|
|
## VCS Tags and Branches
|
|
|
|
*For the following discussion, let's assume the following sample library
|
|
repository:*
|
|
|
|
```sh
|
|
~/my-library$ git branch
|
|
v1
|
|
v2
|
|
my-feature
|
|
nother-feature
|
|
|
|
~/my-library$ git tag
|
|
v1.0
|
|
v1.0.1
|
|
v1.0.2
|
|
v1.1-BETA
|
|
v1.1-RC1
|
|
v1.1-RC2
|
|
v1.1
|
|
v1.1.1
|
|
v2.0-BETA
|
|
v2.0-RC1
|
|
v2.0
|
|
v2.0.1
|
|
v2.0.2
|
|
```
|
|
|
|
### Tags
|
|
|
|
Normally, Composer deals with tags (as opposed to branches -- if you don't
|
|
know what this means, read up on
|
|
[version control systems](https://en.wikipedia.org/wiki/Version_control#Common_vocabulary)).
|
|
When you write a version constraint, it may reference a specific tag (e.g.,
|
|
`1.1`) or it may reference a valid range of tags (e.g., `>=1.1 <2.0`, or
|
|
`~4.0`). To resolve these constraints, Composer first asks the VCS to list
|
|
all available tags, then creates an internal list of available versions based
|
|
on these tags. In the above example, composer's internal list includes versions
|
|
`1.0`, `1.0.1`, `1.0.2`, the beta release of `1.1`, the first and second
|
|
release candidates of `1.1`, the final release version `1.1`, etc.... (Note
|
|
that Composer automatically removes the 'v' prefix in the actual tagname to
|
|
get a valid final version number.)
|
|
|
|
When Composer has a complete list of available versions from your VCS, it then
|
|
finds the highest version that matches all version constraints in your project
|
|
(it's possible that other packages require more specific versions of the
|
|
library than you do, so the version it chooses may not always be the highest
|
|
available version) and it downloads a zip archive of that tag to unpack in the
|
|
correct location in your `vendor` directory.
|
|
|
|
### Branches
|
|
|
|
If you want Composer to check out a branch instead of a tag, you need to point it to the branch using the special `dev-*` prefix (or sometimes suffix; see below). If you're checking out a branch, it's assumed that you want to *work* on the branch and Composer actually clones the repo into the correct place in your `vendor` directory. For tags, it just copies the right files without actually cloning the repo. (You can modify this behavior with --prefer-source and --prefer-dist, see [install options](../03-cli.md#install).)
|
|
|
|
In the above example, if you wanted to check out the `my-feature` branch, you would specify `dev-my-feature` as the version constraint in your `require` clause. This would result in Composer cloning the `my-library` repository into my `vendor` directory and checking out the `my-feature` branch.
|
|
|
|
When branch names look like versions, we have to clarify for composer that we're trying to check out a branch and not a tag. In the above example, we have two version branches: `v1` and `v2`. To get Composer to check out one of these branches, you must specify a version constraint that looks like this: `v1.x-dev`. The `.x` is an arbitrary string that Composer requires to tell it that we're talking about the `v1` branch and not a `v1` tag (alternatively, you can just name the branch `v1.x` instead of `v1`). In the case of a branch with a version-like name (`v1`, in this case), you append `-dev` as a suffix, rather than using `dev-` as a prefix.
|
|
|
|
### Minimum Stability
|
|
|
|
There's one more thing that will affect which files are checked out of a library's VCS and added to your project: Composer allows you to specify stability constraints to limit which tags are considered valid. In the above example, note that the library released a beta and two release candidates for version `1.1` before the final official release. To receive these versions when running `composer install` or `composer update`, we have to explicitly tell Composer that we are ok with release candidates and beta releases (and alpha releases, if we want those). This can be done using either a project-wide `minimum-stability` value in `composer.json` or using "stability flags" in version constraints. Read more on the [schema page](../04-schema.md#minimum-stability).
|
|
|
|
## Writing Version Constraints
|
|
|
|
Now that you have an idea of how Composer sees versions, let's talk about how
|
|
to specify version constraints for your project dependencies.
|
|
|
|
### Exact Version Constraint
|
|
|
|
You can specify the exact version of a package. This will tell Composer to
|
|
install this version and this version only. If other dependencies require
|
|
a different version, the solver will ultimately fail and abort any install
|
|
or update procedures.
|
|
|
|
Example: `1.0.2`
|
|
|
|
### Version Range
|
|
|
|
By using comparison operators you can specify ranges of valid versions. Valid
|
|
operators are `>`, `>=`, `<`, `<=`, `!=`.
|
|
|
|
You can define multiple ranges. Ranges separated by a space (<code> </code>)
|
|
or comma (`,`) will be treated as a **logical AND**. A double pipe (`||`)
|
|
will be treated as a **logical OR**. AND has higher precedence than OR.
|
|
|
|
> **Note:** Be careful when using unbounded ranges as you might end up
|
|
> unexpectedly installing versions that break backwards compatibility.
|
|
> Consider using the [caret](#caret-version-range-) operator instead for safety.
|
|
|
|
Examples:
|
|
|
|
* `>=1.0`
|
|
* `>=1.0 <2.0`
|
|
* `>=1.0 <1.1 || >=1.2`
|
|
|
|
### Hyphenated Version Range ( - )
|
|
|
|
Inclusive set of versions. Partial versions on the right include are completed
|
|
with a wildcard. For example `1.0 - 2.0` is equivalent to `>=1.0.0 <2.1` as the
|
|
`2.0` becomes `2.0.*`. On the other hand `1.0.0 - 2.1.0` is equivalent to
|
|
`>=1.0.0 <=2.1.0`.
|
|
|
|
Example: `1.0 - 2.0`
|
|
|
|
### Wildcard Version Range (.*)
|
|
|
|
You can specify a pattern with a `*` wildcard. `1.0.*` is the equivalent of
|
|
`>=1.0 <1.1`.
|
|
|
|
Example: `1.0.*`
|
|
|
|
## Next Significant Release Operators
|
|
|
|
### Tilde Version Range (~)
|
|
|
|
The `~` operator is best explained by example: `~1.2` is equivalent to
|
|
`>=1.2 <2.0.0`, while `~1.2.3` is equivalent to `>=1.2.3 <1.3.0`. As you can see
|
|
it is mostly useful for projects respecting [semantic
|
|
versioning](http://semver.org/). A common usage would be to mark the minimum
|
|
minor version you depend on, like `~1.2` (which allows anything up to, but not
|
|
including, 2.0). Since in theory there should be no backwards compatibility
|
|
breaks until 2.0, that works well. Another way of looking at it is that using
|
|
`~` specifies a minimum version, but allows the last digit specified to go up.
|
|
|
|
Example: `~1.2`
|
|
|
|
> **Note:** Although `2.0-beta.1` is strictly before `2.0`, a version constraint
|
|
> like `~1.2` would not install it. As said above `~1.2` only means the `.2`
|
|
> can change but the `1.` part is fixed.
|
|
|
|
> **Note:** The `~` operator has an exception on its behavior for the major
|
|
> release number. This means for example that `~1` is the same as `~1.0` as
|
|
> it will not allow the major number to increase trying to keep backwards
|
|
> compatibility.
|
|
|
|
### Caret Version Range (^)
|
|
|
|
The `^` operator behaves very similarly but it sticks closer to semantic
|
|
versioning, and will always allow non-breaking updates. For example `^1.2.3`
|
|
is equivalent to `>=1.2.3 <2.0.0` as none of the releases until 2.0 should
|
|
break backwards compatibility. For pre-1.0 versions it also acts with safety
|
|
in mind and treats `^0.3` as `>=0.3.0 <0.4.0`.
|
|
|
|
This is the recommended operator for maximum interoperability when writing
|
|
library code.
|
|
|
|
Example: `^1.2.3`
|
|
|
|
## Stability Constraints
|
|
|
|
If you are using a constraint that does not explicitly define a stability,
|
|
Composer will default internally to `-dev` or `-stable`, depending on the
|
|
operator(s) used. This happens transparently.
|
|
|
|
If you wish to explicitly consider only the stable release in the comparison,
|
|
add the suffix `-stable`.
|
|
|
|
Examples:
|
|
|
|
Constraint | Internally
|
|
------------------- | ------------------------
|
|
`1.2.3` | `=1.2.3.0-stable`
|
|
`>1.2` | `>1.2.0.0-stable`
|
|
`>=1.2` | `>=1.2.0.0-dev`
|
|
`>=1.2-stable` | `>=1.2.0.0-stable`
|
|
`<1.3` | `<1.3.0.0-dev`
|
|
`<=1.3` | `<=1.3.0.0-stable`
|
|
`1 - 2` | `>=1.0.0.0-dev <3.0.0.0-dev`
|
|
`~1.3` | `>=1.3.0.0-dev <2.0.0.0-dev`
|
|
`1.4.*` | `>=1.4.0.0-dev <1.5.0.0-dev`
|
|
|
|
To allow various stabilities without enforcing them at the constraint level
|
|
however, you may use [stability-flags](../04-schema.md#package-links) like
|
|
`@<stability>` (e.g. `@dev`) to let composer know that a given package
|
|
can be installed in a different stability than your default minimum-stability
|
|
setting. All available stability flags are listed on the minimum-stability
|
|
section of the [schema page](../04-schema.md#minimum-stability).
|
|
|
|
## Summary
|
|
```
|
|
"require": {
|
|
"vendor/package": "1.3.2", // exactly 1.3.2
|
|
|
|
// >, <, >=, <= | specify upper / lower bounds
|
|
"vendor/package": ">=1.3.2", // anything above or equal to 1.3.2
|
|
"vendor/package": "<1.3.2", // anything below 1.3.2
|
|
|
|
// * | wildcard
|
|
"vendor/package": "1.3.*", // >=1.3.0 <1.4.0
|
|
|
|
// ~ | allows last digit specified to go up
|
|
"vendor/package": "~1.3.2", // >=1.3.2 <1.4.0
|
|
"vendor/package": "~1.3", // >=1.3.0 <2.0.0
|
|
|
|
// ^ | doesn't allow breaking changes (major version fixed - following semver)
|
|
"vendor/package": "^1.3.2", // >=1.3.2 <2.0.0
|
|
"vendor/package": "^0.3.2", // >=0.3.2 <0.4.0 // except if major version is 0
|
|
}
|
|
```
|
|
|
|
## Testing Version Constraints
|
|
|
|
You can test version constraints using [semver.mwl.be](https://semver.mwl.be).
|
|
Fill in a package name and it will autofill the default version constraint
|
|
which Composer would add to your `composer.json` file. You can adjust the
|
|
version constraint and the tool will highlight all releases that match.
|