Makes `createProperty` easier to use to customize properties #914

sorvell · 2020-03-05T22:42:47Z

Fixes #911. It is now easier to override property accessor creation. A new static getPropertyDescriptor(name: PropertyKey, key: string|symbol, options: PropertyDeclaraction) is added here. This method should return a property descriptor to use when defining the property. If no descriptor is returned, the property will not become an accessor.

Example:

class MyElement extends LitElement {
  static getPropertyDescriptor(
      name: PropertyKey,
      key: string|symbol,
      options: PropertyDeclaration) {

    const defaultDescriptor = super.getPropertyDescriptor(name, key, options); 
    const setter = defaultDescriptor.set;
    return Object.assign(descriptor, {
      set(this: MyElement, value: unknown) {
        setter.call(this, value);
        console.log('Property', name, 'was set to', value);
     }
  }
  //...
}

Fixes #905. A couple changes to make customizing property accessors easier. * Adds static methods`setOptionsForProperty(name, options)`, `getOptionsForProperty` and renames `_requestUpdate` to `requestUpdateInternal` and makes it protected. With these changes, users can override `createProperty` and (1) pass in and later retrieve custom property otions, (2) customize how accessors are defined and call `requestUpdateInternal` in the setter to make the property reactive.

This function receives the property declaration, key of the private storage for the property, and default property descriptor. It should return a PropertyDescriptor. Users can customer this descriptor to control how property accessors behave.

src/lib/updating-element.ts

This method is called internallly by `createProperty` to get a descriptor to install on the property. Users can implement it to customize what property accessors do.

Users can implement setters with `requestUpdate`.

src/lib/updating-element.ts

src/test/lib/updating-element_test.ts

src/lib/updating-element.ts

kevinpschaaf

LGTM

Ping @justinfagnani to weigh in on getPropertyOptions vs. getDeclarationForProperty naming before it's too late... "Declaration" is a sort of obtuse name for the options, and we call the argument options throughout the code, but we've already grandfathered "Declaration" in the type. I like options better, but I can see a consistency argument either way.

justinfagnani

Looks good as-is, but I had a couple of small naming questions.

justinfagnani · 2020-03-10T01:24:23Z

src/lib/updating-element.ts

+   *
+   * Note, this method should be considered "final" and not overridden. To
+   * customize the options for a given property, override `createProperty`.
+   *


Maybe add a @final annotation. Not sure if these flow through from TypeScript to Closure via tsickle or not, but it doesn't hurt.

justinfagnani · 2020-03-10T01:25:29Z

src/lib/updating-element.ts

+   * customize the options for a given property, override `createProperty`.
+   *
+   */
+  protected static getPropertyOptions(name: PropertyKey) {


Can this be private? It seems to only be accessed from other private methods. If so, rename to _getPropertyOptions

It's protected so options can be used in the element lifecycle. For example, in updated you might want to act on a given changed property if it has a specific option.

justinfagnani · 2020-03-10T01:26:43Z

src/lib/updating-element.ts

+   *
+   * @nocollapse
+   */
+  protected static createPropertyDescriptor(name: PropertyKey,


Should we name this get...? On getX vs. createX it seems like the distinction is that createX is side effectful and getX isn't.

Steven Orvell added 5 commits February 28, 2020 17:21

Adds tests for property customization

97789b5

Chage argument order.

45ede17

Update CHANGELOG.md

5e317f6

sorvell requested review from justinfagnani and kevinpschaaf March 5, 2020 22:42

googlebot added the cla: yes label Mar 5, 2020

Steven Orvell added 2 commits March 5, 2020 15:00

Lint fix.

e2ef7d9

Expands property customization test

d0ecc90

justinfagnani requested changes Mar 9, 2020

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Steven Orvell added 4 commits March 9, 2020 10:35

Improved type.

b96a366

Adds createPropertyDescriptor(name, key, options)

a33f63f

This method is called internallly by `createProperty` to get a descriptor to install on the property. Users can implement it to customize what property accessors do.

Switch back to private _requestUpdate

5479afa

Users can implement setters with `requestUpdate`.

Adds API doc for createPropertyDescriptor

734adc5

kevinpschaaf reviewed Mar 9, 2020

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Steven Orvell added 4 commits March 9, 2020 17:14

Address review feedback.

297b8b2

Fix spacing.

def6df1

Fix spacing.

ec9048b

Update comment.

8f5815f

kevinpschaaf approved these changes Mar 10, 2020

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justinfagnani approved these changes Mar 10, 2020

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Address review feedback.

90c85a5

sorvell merged commit 8055b93 into master Mar 10, 2020

sorvell deleted the customize-properties branch March 10, 2020 19:58

justinfagnani mentioned this pull request Mar 14, 2020

Can we help you possibly use LitElement? Netflix/x-element#53

Open

sorvell mentioned this pull request Mar 17, 2020

PropertyDeclaration added index signature incompatible with previous type #928

Closed

kevinpschaaf mentioned this pull request Apr 14, 2020

Makes performUpdate possible to call synchronously #959

Merged

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Makes `createProperty` easier to use to customize properties #914

Makes `createProperty` easier to use to customize properties #914

sorvell commented Mar 5, 2020 •

edited by kevinpschaaf

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Makes createProperty easier to use to customize properties #914

Makes createProperty easier to use to customize properties #914

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Makes `createProperty` easier to use to customize properties #914

Makes `createProperty` easier to use to customize properties #914

sorvell commented Mar 5, 2020 •

edited by kevinpschaaf

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