This PR improves where we inject the border compatibility CSS. Before
this change we injected it if it was necessary in one of these spots:
- Above the first `@layer base` to group it together with existing
`@layer base` at-rules.
- If not present, after the last `@import`, to make sure that we emit
valid CSS because `@import` should be at the top (with a few
exceptions).
However, if you are working with multiple CSS files, then it could be
that we injected the border compatibility CSS multiple times if those
files met one of the above conditions.
To solve this, we now inject the border compatibility CSS with the same
rules as above, but we also have another condition:
The border compatibility CSS is only injected if the file also has a
`@import "tailwindcss";` _or_ `@import "tailwindcss/preflight";` in the
current file.
---
Added integration tests to make sure that we are generating what we
expect in a real environment. Some of the integration tests also use the
old `@tailwind` directives to make sure that the order of migrations is
correct (first migrate to `@import` syntax, then inject the border
compatibility CSS).
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Co-authored-by: Adam Wathan <adam.wathan@gmail.com>
This PR adds a codemod that ensures that the border styles from Tailwind CSS v3 work as expected once your project is migrated to Tailwind CSS v4.
In Tailwind CSS v3, the default border color is `colors.gray.200` and in Tailwind CSS v4 the default border color is `currentColor`.
Similarly in Tailwind CSS v3, DOM elements such as `input`, `select`, and `textarea` have a border width of `0px`, in Tailwind CSS v4, we don't change the border width of these elements and keep them as `1px`.
If your project happens to already use the same value for the default border color (`currentColor`) as we use in Tailwind CSS v4, then nothing happens. But this is very unlikely, so we will make sure that we honor your `borderColor.DEFAULT` value.
If you didn't change the default values in your `tailwind.config.js`, then we will inject compatibility CSS using the default Tailwind CSS v3 values to ensure the default color and width are applied correctly.
