Migration from UI Patterns 1
Ecosystem consolidation
If you are coming from UI Patterns 1.x, you may not find UI Patterns 2.x version of your favourite modules on https://www.drupal.org/project/project_module
Maybe because it was merged into an UI Patterns 2.x sub-module:

So, you can now found most of the UI Patterns integration inside the main ui_patterns project and 2 sub-modules were moved out of the project:
- Display Suite. Now found in https://www.drupal.org/project/ui_patterns_ds
 - Field Group. Now found in https://www.drupal.org/project/ui_patterns_field_group
 
Automatic components migration
You need to activate ui_patterns_legacy sub-module.
And run:
drush ui-patterns:migrate my_theme
Or:
drush upm my_theme
The converted components can be found in components/. patterns/ folder is kept by the migration, but can be removed.
Component definitions
It is done automatically by the drush command:
- "fields" are becoming slots
 - "settings" are becoming props
 
| UIP 1.x setting type | UIP2 2.x prop type | 
|---|---|
| Attributes | attributes | 
| Boolean | boolean | 
| Checkboxes | list | 
| Links | links | 
| Machine Name | identifier | 
| Number | number | 
| Radios | enum | 
| Select | enum | 
| Textfield | string | 
| Token | string | 
| Url | url | 
⚠️ Some features, mixing data structure and data sources, don't make sense with SDC and are ignored during migration:
allow_variant_token(on component level) andallow_token(on setting level): Replaced by the Token source plugin used with the Variant or any other prop type.allow_variant_expose(on component level) andallow_variant_expose(on setting level): Replaced by theui_patterns_sourcefield type (expected for UI Patterns 2.1). You can attach a ui_patterns_source field and select the variant or any other property in the field widget and display this field inside your entity form.expose_as_field(on setting level): Also replaced by theui_patterns_sourcefield type. Mapping a property to a specific field is removed.
Anyway, there are a few tasks you may want to do after that:
identifier props
In UI Patterns 1.x, machine_name setting type was overlooked because:
- it was added late (mid 2023)
 - it was not compatible with the broadly used 
tokensource 
In UI Patterns 2.x, it was replaced by identifier prop type can be used without those limitations.
number props
In UI Patterns 1.x, number setting type doesn't allow to tell when a number is a decimal or an integer.
In UI Patterns 2.x, you can replace type: number by type: integer.
Ignored setting types
Those settings are not migrated:
- ColorWidget
 - ColorisWidget
 - GroupType
 - LanguageCheckboxes
 - LanguageAccess
 - MediaLibrary
 - Publish
 
Templates
The templates are exactly the same between UI Patterns 1.x and UI Patterns 2.x, except pattern() function which has been replaced by the Twig native include() function:
pattern(
  "card",
  {slot_1: foo, slot_2: bar, prop_1: baz, prop_2: true},
  variant_id
)
becomes:
include(
  "bootstrap:card",
  {slot_1: foo, slot_2: bar, prop_1: baz, prop_2: true, variant: variant_id},
  with_context = false
)
Differences:
component_idis now prefixed by the provider (theme or module)variantis now a prop instead of a function parameterwith_context = falsemust be added to avoid scope leaks.
Until the manual conversion is done, you can still use pattern() thanks to a compatibility layer, if you keep ui_patterns_legacy activated.
⚠️ variants templates (ex:
pattern-card--variant-horizontal.html.twig) are not kept because they don't exist in UI Patterns 2
Preview/Stories
A story called preview is automatically created from all the preview values extracted from the component definition.
For example, this UI Patterns 1.x definition:
button:
  label: "Button"
  settings:
    disabled:
      type: "boolean"
      label: "Disabled?"
      preview: false
      allow_token: true
    label_visually_hidden:
      type: "boolean"
      label: "Hide button label?"
      preview: false
    url:
      type: "url"
      label: "URL"
      preview: "https://example.com"
  fields:
    label:
      type: "text"
      label: "Label"
      preview: "Submit"
Is becoming this story:
name: Preview
slots:
  label: Submit
props:
  disabled: false
  label_visually_hidden: false
  url: "https://example.com"
Preview templates
Preview templates (pattern-{component_id}--preview.html.twig) are replaced by library_wrapper properties of story definition, but this is not done automatically.
Compatibility layer at runtime
By keeping ui_patterns_legacy activated after the migration, you can leverage a compatibility layer between UI Patterns 1.x and SDC API.
Render elements
For example, this render element:
[
  '#type' => 'pattern',
  '#id' => 'blockquote',
  '#variant' => 'highlighted',
  '#fields' => [
    'quote' => 'You must do the things you think you cannot do.',
    'attribution' => 'Eleanor Roosevelt',
   ],
  '#settings' => [
     'url' => 'https://example.org'
  ]
]
And this one:
[
  '#type' => 'pattern',
  '#id' => 'blockquote',
  '#variant' => 'highlighted',
  'quote' => 'You must do the things you think you cannot do.',
  'attribution' => 'Eleanor Roosevelt',
   'url' => 'https://example.org'
]
Are both converted to:
[
  '#type' => 'component',
  '#component' => 'provider:blockquote',
  '#slots' => [
    'quote' => 'You must do the things you think you cannot do.',
    'attribution' => 'Eleanor Roosevelt',
   ],
  '#props' => [
     'url' => 'https://example.org',
     'variant' => 'highlighted'
  ]
]
It works also for pattern_preview render element:
[
  '#type' => 'pattern_preview',
  '#id' => 'blockquote',
  '#variant' => 'highlighted',
]
Is converted at runtime to:
[
  '#type' => 'component',
  '#component' => 'provider:blockquote',
  '#story' => 'preview',
  '#props' => [
     'variant' => 'highlighted'
  ]
]
Twig functions
At runtime, pattern() twig function:
pattern(
  "card",
  {slot_1: foo, slot_2: bar, prop_1: baz, prop_2: true},
  variant_id
)
is processed as:
[
  '#type' => 'component',
  '#component' => 'bootstrap:card',
  '#slots' => [
    'slot_1' => foo,
    'slot_2' => bar,
   ],
  '#props' => [
     'prop_1' => 'baz',
     'prop_2' => true,
     'variant' => 'variant_id'
  ]
]
⚠️ The provider is guessed. If you have many components with the same ID (so, in this example, many cards), the provider may be guessed wrong.
Same for pattern_preview:
{{ pattern_preview('modal', 'highlighted') }}
is processed as:
[
  '#type' => 'component',
  '#component' => 'provider:modal',
  '#story' => 'preview',
  '#props' => [
     'variant' => 'variant_id'
  ]
]