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Bootstrap 5 migration

Bootstrap 5 has evolved with new features, improvements, and changes in its latest version, and along with this some breaking changes also come, which need to be addressed in the migration process.

info

See more about Bootstrap 5 breaking changes in the official documentation.

To achieve a smoother process and facilitate the moment of the update, the migration has been divided into different steps:

  1. PopperJS upgrade: This is the first step in the migration process, as Bootstrap 5 requires PopperJS version 2. This step is about upgrading the current PopperJS version to version 2. Because we still need PopperJS version 1 for Bootstrap 4 both versions will co-exist until all usages are migrated to v2.
  2. SCSS Deprecation process: A SCSS deprecation process will be needed for the cleanup after BS5 upgrade. More details about it in SCSS deprecation.
  3. Refactoring BS4 features dropped in BS5: This step is about refactoring the current Bootstrap 4 features that will be deprecated or dropped in its version 5 and they can be replaced with current codebase.
  4. Create a BS5 "bridge": Some simple breaking changes could be also addressed in advance creating a BS5 "bridge". With small additions to this "bridge", we can refactor in advance the occurrences in the codebase for some dropped features in BS5.
  5. BS5 upgrade: Upgrade the current Bootstrap 4 version to version 5.
  6. BS4 backwards-compatibility layer: Alongside the update, a new backwards-compatibility layer will also be created, and some of the Bootstrap 4 syntax will still work until the final deprecation. This will help third-party plugins to be updated in a more gradual way.
  7. Final deprecation
note

The migration process will be done in a gradual way, and the steps will be executed in different phases. The first phase with the PopperJS upgrade, the SCSS deprecation process and the refactoring will be included in Moodle 4.4. The other steps will be ready in following releases. This documentation page will be updated accordingly with the process.

Refactoring BS4 features dropped in BS5​

Since 4.4

Some of the Bootstrap 4 classes will be deprecated or dropped in its version 5. To prepare for this, some of the current Bootstrap 4 classes usages have been replaced with version 5 compatible classes. Doing these refactors in advance, will help us to upgrade to Bootstrap 5 in the future.

Badges​

  • Badge colour class helpers .badge-* have been replaced with background utilities (use .bg-primary instead of .badge-primary) combined with the corresponding text colour classes (.text-dark or .text-white) to meet accessibility contrast.
  • The .badge-pill class has been replaced with .rounded-pill
Don't
<span class="badge badge-danger badge-pill">Error badge</span>
Do
<span class="badge bg-danger text-white rounded-pill">Error badge</span>

Media​

The .media component has been replaced with utility classes.

Don't
<div class="media">
    <div class="media-left">
        [...]
    </div>
    <div class="media-body">
        [...]
    </div>
</div>
Do
<div class="d-flex">
    <div class="flex-shrink-0">
        [...]
    </div>
    <div class="flex-grow-1 ml-3">
        [...]
    </div>
</div>

Mixins​

The following previously deprecated mixins will be dropped in BS5, so they can be refactored:

  • hover, hover-focus, plain-hover-focus and hover-focus-active
  • float-left, float-right and float-none
  • nav-divider
  • img-retina
  • text-hide
  • invisible
  • form-control-focus
  • text-emphasis-variant
  • size
  • make-container-max-widths
  • g-variant and bg-gradient-variant
Don't
.collapse-list-item {
    padding: $collapse-list-item-padding-y $collapse-list-item-padding-x;
    @include hover-focus() {
        background-color: $collapse-list-item-hover-bg;
        border-color: $collapse-list-item-hover-border;
    }
}
Do
.collapse-list-item {
    padding: $collapse-list-item-padding-y $collapse-list-item-padding-x;
    &:hover,
    &:focus {
        background-color: $collapse-list-item-hover-bg;
        border-color: $collapse-list-item-hover-border;
    }
}

Forms​

  • The .form-group helper class has been replaced with margins.
  • The .form-inline helper class has been replaced with utility classes.
Don't
<form class="form-inline">
    <div class="form-group">
        [...]
    </div>
</form>
Do
<form class="d-flex flex-wrap align-items-center">
    <div class="mb-3">
        [...]
    </div>
</form>

Card decks​

The .card-deck helper class has been replaced with utility classes.

Don't
<div class="card-deck">
    <div class="card">
        [...]
    </div>
    <div class="card">
        [...]
    </div>
</div>
Do
<div class="row row-cols-1 row-cols-sm-2">
    <div class="col">
        <div class="card">
            [...]
        </div>
    </div>
    <div class="col">
        <div class="card">
            [...]
        </div>
    </div>
</div>

Create a BS5 "bridge"​

Since 4.5

Some simple breaking changes could be also addressed in advance creating a BS5 "bridge". With small additions to this "bridge", we can refactor in advance the occurrences in the codebase for some dropped or changed features in BS5.

A new SCSS file bs5-bridge.scss has been created in the theme/boost/scss/moodle folder. This file will contain the necessary changes to make the codebase compatible with Bootstrap 5.

Example of a bridge in bs5-bridge.scss
/* In Bootstrap 5 the .no-gutters class has been replaced with .g-0, so we can
add a new class in the bridge file to make the codebase compatible with BS5. */
.g-0 {
    @extend .no-gutters;
}

No gutters​

The .no-gutters grid class has been replaced with .g-0.

Don't
<div class="row no-gutters">
    <div class="col-6">[...]</div>
    <div class="col-6">[...]</div>
</div>
Do
<div class="row g-0">
    <div class="col-6">[...]</div>
    <div class="col-6">[...]</div>
</div>

Close button​

The .close class has been replaced with .btn-close.

Don't
<div class="alert alert-warning alert-dismissible" role="alert">
  I'm an alert.
  <button type="button" class="close" data-dismiss="alert" aria-label="Close">
    <span aria-hidden="true">&times;</span>
  </button>
</div>
Do
<div class="alert alert-warning alert-dismissible" role="alert">
  I'm an alert.
  <button type="button" class="btn-close" data-dismiss="alert" aria-label="Close">
    <span aria-hidden="true">&times;</span>
  </button>
</div>

Directional utilities​

Several utilities have been renamed to use logical property names instead of directional ones.

  • Renamed .float-left and .float-right to .float-start and .float-end.
  • Renamed .border-left and .border-right to .border-start and .border-end.
  • Renamed .rounded-left and .rounded-right to .rounded-start and .rounded-end.
  • Renamed .ml-* and .mr-* to .ms-* and .me-*.
  • Renamed .pl-* and .pr-* to .ps-* and .pe-*.
  • Renamed .text-left and .text-right to .text-start and .text-end.
Don't
<div class="ml-3 pr-sm-3">
    <div class="border-left text-left">[...]</div>
    <div class="float-right mr-auto">[...]</div>
</div>
Do
<div class="ms-3 pe-sm-3">
    <div class="border-start text-start">[...]</div>
    <div class="float-end me-auto">[...]</div>
</div>

Theme color level​

In Bootstrap 4.x we used a function called theme-color-level() which was removed in Bootstrap 5. The prototype of the function was:

Previous version using theme-color-level()
@function theme-color-level($colorname, $level) {
    [...]
}
[...]
theme-color-level('primary', 1);

The replacement is now shift-color(). This function is used to shift a color by a percentage (weight) of shades. So, two major difference in the new version:

  • we use the color definition instead of the color name
  • we use percentages instead of levels.
Current version using shift-color()
@function shift-color($color, $weight) {
   [...]
}
[...]
shift-color($primary, 10%);

As we transitioned from using levels to percentages, the parameters have changed. So instead of working with numbers (1 to 11), we now use percentages. To simplify this transition, Bootstrap 5 has established a new equivalency: each level increment from 1 now corresponds to a 10% shift.

From absolute levels to percentages

For example, if a theme-color-level was previously set to a value of 1, it will now be set to 10%. A level of two will be adjusted by 20% and so on.

We can use the following formula to convert the level to percentage:

Don't
theme-color-level('primary', 1)
theme-color-level('primary', -2)
Do
shift-color($primary, 10%);
shift-color($primary, -20%);
note

The theme-color-level() has been changed to color-level() and then subsequently removed and replaced by scale-color(). In the stable 5.0 the final decision was to adopt shift-color() so we will use this function in the bridge file.