This PR adds a new migration that can migrate Tailwind CSS v3 style
prefixes into Tailwind CSS v4.
The migration is split into three separate pieces of work:
1. Firstly, we need to read the full JavaScript config to get the _old_
prefix option. This is necessary because in v4, we will not allow things
like custom-separators for the prefix. From this option we will then try
and compute a new prefix (in 90% of the cases this is going to just
remove the trailing `-` but it can also work in more complex cases).
2. Then we migrate all Candidates. The important thing here is that we
need to operate on the raw candidate string because by relying on
`parseCandidate` (which we do for all other migrations) would not work,
as the candidates are not valid in v4 syntax. More on that in a bit.
3. Lastly we also make sure to update the CSS config to include the new
prefix. This is done by prepending the prefix option like so:
```css
@import "tailwindcss" prefix(tw);
```
### Migrating candidates
The main difference between v3 prefixes and v4 prefixes is that in v3,
the prefix was _part of the utility_ where as in v4 it is _always in
front of the CSS class.
So, for example, this candidate in v3:
```
hover:-tw-mr-4
```
Would be converted to the following in v4:
```
tw:hover:-mr-4
```
Since the first example _won't parse as a valid Candidate in v4, as the
`tw-mr` utility does not exist, we have to operate on the raw candidate
string first. To do this I created a fork of the `parseCandidate`
function _without any validation of utilities or variants_. This is used
to identify part of the candidate that is the `base` and then ensuring
the `base` starts with the old prefix. We then remove this to create an
"unprefixed" candidate that we validate against a version of the
DesignSystem _with no prefixes configured_. If the variant is valid this
way, we can then print it again with the `DesignSystem` that has the new
prefix to get the migrated version.
Since we set up the `DesignSystem` to include the new prefix, we can
also be certain that migrations that happen afterwards would still
disqualify candidates that aren't valid according to the new prefix
policy. This does mean we need to have the prefix fixup be the first
step in our pipeline.
One interesting bit is that in v3, arbitrary properties did not require
prefixes where as in v4 they do. So the following candidate:
```
[color:red]
```
Will be converted to:
```
tw:[color:red]
```
This PR adds the initial setup and a first codemod for the template
migrations. These are a new set of migrations that operate on files
defined in the Tailwind v3 config as part of the `content` option (so
your HTML, JavaScript, TSX files etc.).
The migration for this is integrated in the new `@tailwindcss/upgrade`
package and will require pointing the migration to an input JavaScript
config file, like this:
```
npx @tailwindcss/upgrade --config tailwind.config.js
```
The idea of template migrations is to apply breaking changes from the v3
to v4 migration within your template files.
## Migrating !important syntax
The first migration that I’m adding with this PR is to ensure we use the
v4 important syntax that has the exclamation mark at the end of the
utility.
For example, this:
```html
<div class="!flex sm:!block"></div>
```
Will now turn into:
```html
<div class="flex! sm:block!"></div>
```
## Architecture considerations
Implementation wise, we make use of Oxide to scan the content files fast
and efficiently. By relying on the same scanner als Tailwind v4, we
guarantee that all candidates that are part of the v4 output will have
gone through a migration.
Migrations itself operate on the abstract `Candidate` type, similar to
the type we use in the v4 codebase. It will parse the candidate into its
parts so they can easily be introspected/modified. Migrations are typed
as:
```ts
type TemplateMigration = (candidate: Candidate) => Candidate | null
```
`null` should be returned if the `Candidate` does not need a migration.
We currently use the v4 `parseCandidate` function to get an abstract
definition of the candidate rule that we can operate on. _This will
likely need to change in the future as we need to fork `parseCandidate`
for v3 specific syntax_.
Additionally, we're inlining a `printCandidate` function that can
stringify the abstract `Candidate` type. It is not guaranteed that this
is an identity function since some information can be lost during the
parse step. This is not a problem though, because migrations will only
run selectively and if none of the selectors trigger, the candidates are
not updated. h/t to @RobinMalfait for providing the printer.
So the overall flow of a migration looks like this:
- Scan the config file for `content` files
- Use Oxide to extract a list of candidate and their positions from
these `content` files
- Run a few migrations that operate on the `Candidate` abstract type.
- Print the updated `Candidate` back into the original `content` file.
---------
Co-authored-by: Robin Malfait <malfait.robin@gmail.com>
Co-authored-by: Jordan Pittman <jordan@cryptica.me>
This PR adds CSS codemods for migrating existing `@layer utilities` to
`@utility` directives.
This PR has the ability to migrate the following cases:
---
The most basic case is when you want to migrate a simple class to a
utility directive.
Input:
```css
@layer utilities {
.foo {
color: red;
}
.bar {
color: blue;
}
}
```
Output:
```css
@utility foo {
color: red;
}
@utility bar {
color: blue;
}
```
You'll notice that the class `foo` will be used as the utility name, the
declarations (and the rest of the body of the rule) will become the body
of the `@utility` definition.
---
In v3, every class in a selector will become a utility. To correctly
migrate this to `@utility` directives, we have to register each class in
the selector and generate `n` utilities.
We can use nesting syntax, and replace the current class with `&` to
ensure that the final result behaves the same.
Input:
```css
@layer utilities {
.foo .bar .baz {
color: red;
}
}
```
Output:
```css
@utility foo {
& .bar .baz {
color: red;
}
}
@utility bar {
.foo & .baz {
color: red;
}
}
@utility .baz {
.foo .bar & {
color: red;
}
}
```
In this case, it could be that you know that some of them will never be
used as a utility (e.g.: `hover:bar`), but then you can safely remove
them.
---
Even classes inside of `:has(…)` will become a utility. The only
exception to the rule is that we don't do it for `:not(…)`.
Input:
```css
@layer utilities {
.foo .bar:not(.qux):has(.baz) {
display: none;
}
}
```
Output:
```css
@utility foo {
& .bar:not(.qux):has(.baz) {
display: none;
}
}
@utility bar {
.foo &:not(.qux):has(.baz) {
display: none;
}
}
@utility baz {
.foo .bar:not(.qux):has(&) {
display: none;
}
}
```
Notice that there is no `@utility qux` because it was used inside of
`:not(…)`.
---
When classes are nested inside at-rules, then these classes will also
become utilities. However, the `@utility <name>` will be at the top and
the at-rules will live inside of it. If there are multiple classes
inside a shared at-rule, then the at-rule will be duplicated for each
class.
Let's look at an example to make it more clear:
Input:
```css
@layer utilities {
@media (min-width: 640px) {
.foo {
color: red;
}
.bar {
color: blue;
}
@media (min-width: 1024px) {
.baz {
color: green;
}
@media (min-width: 1280px) {
.qux {
color: yellow;
}
}
}
}
}
```
Output:
```css
@utility foo {
@media (min-width: 640px) {
color: red;
}
}
@utility bar {
@media (min-width: 640px) {
color: blue;
}
}
@utility baz {
@media (min-width: 640px) {
@media (min-width: 1024px) {
color: green;
}
}
}
@utility qux {
@media (min-width: 640px) {
@media (min-width: 1024px) {
@media (min-width: 1280px) {
color: yellow;
}
}
}
}
```
---
When classes result in multiple `@utility` directives with the same
name, then the definitions will be merged together.
Input:
```css
@layer utilities {
.no-scrollbar::-webkit-scrollbar {
display: none;
}
.no-scrollbar {
-ms-overflow-style: none;
scrollbar-width: none;
}
}
```
Intermediate representation:
```css
@utility no-scrollbar {
&::-webkit-scrollbar {
display: none;
}
}
@utility no-scrollbar {
-ms-overflow-style: none;
scrollbar-width: none;
}
```
Output:
```css
@utility no-scrollbar {
&::-webkit-scrollbar {
display: none;
}
-ms-overflow-style: none;
scrollbar-width: none
}
```
---------
Co-authored-by: Jordan Pittman <jordan@cryptica.me>
This PR adds some initial tooling for codemods. We are currently only
interested in migrating CSS files, so we will be using PostCSS under the
hood to do this. This PR also implements the "migrate `@apply`" codemod
from #14412.
The usage will look like this:
```sh
npx @tailwindcss/upgrade
```
You can pass in CSS files to transform as arguments:
```sh
npx @tailwindcss/upgrade src/**/*.css
```
But, if none are provided, it will search for CSS files in the current
directory and its subdirectories.
```
≈ tailwindcss v4.0.0-alpha.24
│ No files provided. Searching for CSS files in the current
│ directory and its subdirectories…
│ Migration complete. Verify the changes and commit them to
│ your repository.
```
The tooling also requires the Git repository to be in a clean state.
This is a common convention to ensure that everything is undo-able. If
we detect that the git repository is dirty, we will abort the migration.
```
≈ tailwindcss v4.0.0-alpha.24
│ Git directory is not clean. Please stash or commit your
│ changes before migrating.
│ You may use the `--force` flag to override this safety
│ check.
```
---
This PR alsoo adds CSS codemods for migrating existing `@apply`
directives to the new version.
This PR has the ability to migrate the following cases:
---
In v4, the convention is to put the important modifier `!` at the end of
the utility class instead of right before it. This makes it easier to
reason about, especially when you are variants.
Input:
```css
.foo {
@apply !flex flex-col! hover:!items-start items-center;
}
```
Output:
```css
.foo {
@apply flex! flex-col! hover:items-start! items-center;
}
```
---
In v4 we don't support `!important` as a marker at the end of `@apply`
directives. Instead, you can append the `!` to each utility class to
make it `!important`.
Input:
```css
.foo {
@apply flex flex-col !important;
}
```
Output:
```css
.foo {
@apply flex! flex-col!;
}
```
