✨PWA: Expose amp-bind getState and setState #25011

mattwomple · 2019-10-10T20:47:37Z

Allow PWAs to access amp-bind methods through the shadowDoc instance created by AMP.attachShadowDoc():

shadowDoc.getState(expr) - Get an amp-bind state from the AMP document using a JSON expression string
shadowDoc.setState(state) - Deep merge an object or expression into the AMP document's global amp-bind state

Expose shadowDoc.getState and shadowDoc.setState methods for PWAs.

mattwomple · 2019-10-10T20:48:46Z

@choumx Initial thoughts welcome. I'm actually blocked on testing .setState because this promise seems to hang (at least in localhost testing):

amphtml/extensions/amp-bind/0.1/bind-impl.js

Line 1024 in bcdd618

const evaluatePromise = this.ww_('bind.evaluateBindings', [this.state_]);

Oh, I see, ww.js isn't lazy building: GET http://localhost:8000/dist/ww.js net::ERR_EMPTY_RESPONSE

mattwomple · 2019-10-11T09:11:32Z

src/runtime.js

+       * a copy of the value of a state
+       */
+      getState: name => {
+        return Services.bindForDocOrNull(shadowRoot).then(bind => {


For pages that do not use amp-bind, this promise never resolves. I don't think it's a problem, but wanted to make sure this received consideration.

Hm, it should resolve with null on pages that are missing the extension script in the doc head.

mattwomple · 2019-10-11T09:11:44Z

src/runtime.js

+       * @return {Promise} - Resolves after state and history have been updated
+       */
+      setState: state => {
+        return Services.bindForDocOrNull(shadowRoot).then(bind => {


extensions/amp-bind/0.1/bind-impl.js

mattwomple · 2019-10-14T18:52:43Z

src/runtime.js

+       */
+      getState: name => {
+        return Services.bindForDocOrNull(shadowRoot).then(bind => {
+          return bind && bind.getStateCopy(name);


This should probably be changed to:
return bind ? bind.getStateCopy(name) : Promise.resolve();

mattwomple · 2019-10-14T18:54:52Z

src/runtime.js

+        return Services.bindForDocOrNull(shadowRoot).then(bind => {
+          return (
+            (bind && bind.setStateAndUpdateHistory(state)) || Promise.resolve()
+          );


This would be more readable as:
return bind ? bind.setStateAndUpdateHistory(state) : Promise.resolve();

dreamofabear

Thanks for taking this on!

dreamofabear · 2019-10-14T18:48:45Z

spec/amp-shadow-doc.md

@@ -94,6 +94,8 @@ Both `AMP.attachShadowDoc` and `AMP.attachShadowDocAsStream` return a `ShadowDoc
 - `shadowDoc.setVisibilityState()` - changes the visibility state of the AMP document.
 - `shadowDoc.postMessage()` and `shadowDoc.onMessage()` - can be used to message with the AMP document.
 - `shadowDoc.close()` - closes the AMP document and frees the resources.
+- `shadowDoc.bind.getState(expr)` - Get an `amp-bind` state from the AMP document using expression syntax
+- `shadowDoc.bind.setState(obj)` - Deep merge an object into the AMP document's global `amp-bind` state


IMO it's fine to not namespace this under .bind since we don't namespace the on="tap:AMP.setState(...)" action either.

dreamofabear · 2019-10-14T18:49:00Z

spec/amp-shadow-doc.md

@@ -94,6 +94,8 @@ Both `AMP.attachShadowDoc` and `AMP.attachShadowDocAsStream` return a `ShadowDoc
 - `shadowDoc.setVisibilityState()` - changes the visibility state of the AMP document.
 - `shadowDoc.postMessage()` and `shadowDoc.onMessage()` - can be used to message with the AMP document.
 - `shadowDoc.close()` - closes the AMP document and frees the resources.
+- `shadowDoc.bind.getState(expr)` - Get an `amp-bind` state from the AMP document using expression syntax


Let's mention that expr is a JSON expression string e.g. "foo.bar".

dreamofabear · 2019-10-14T18:49:39Z

extensions/amp-bind/0.1/bind-impl.js

+   * @param {string} expr
+   * @return {(?JsonObject|string|undefined)}
+   */
+  getStateCopy(expr) {


Nit: Let's just call this getState(). There shouldn't be a use case for returning a non-copy.

dreamofabear · 2019-10-14T18:55:42Z

extensions/amp-bind/0.1/bind-impl.js

+    // Support expressions
+    if (typeof state === 'string') {
+      // Emulate UIEvent 'click'
+      return this.pushStateWithExpression(


A bit confusing if this API can both "set" and "push" state. I think it's worth separating into two APIs.

Though for the sake of keeping this PR small, can we remove this case?

To make sure I understand, are you suggesting that we do not update history with the shadowDoc.setState() method?

I mean removing this case where passing a string calls "push" instead of "set". The former appends a new entry onto the history stack.

Or maybe you just meant to call setStateWithExpression here?

dreamofabear · 2019-10-14T18:56:38Z

extensions/amp-bind/0.1/bind-impl.js

+          this.history_.replace(data);
+        }
+      });
+    return this.setStatePromise_;


Would be nice to de-dupe this code snippet with setStateWithExpression. Feel free to create a new private helper method or just drop a TODO(choumx) here for me.

mattwomple · 2019-10-14T23:28:52Z

Thank you for the review! I believe all review comments are resolved in 1a1582e.

dreamofabear

Looks good overall.

/cc @dvoytenko FYI a new shadow API for amp-bind.

dreamofabear · 2019-10-15T19:34:54Z

src/runtime.js

+          // Emulate UIEvent 'click'
+          return bind.setStateWithExpression(
+            /** @type {string} */ (state),
+            /** @type {!JsonObject} */ ({event: 1})


Is {event: 1} useful here?

I haven't dug too deep into how the scope parameter is used, but at least an empty object needs to be passed. I opted to mimic the object that is passed by a single click event here.

Empty object will suffice then. :)

It's used for things like on="submit-success: AMP.setState({foo: event.response})", but there's no real "event context" in this case.

dvoytenko

API LGTM

dreamofabear · 2019-10-16T15:28:09Z

Great contribution!

* PWA: Expose getState and setState Expose shadowDoc.getState and shadowDoc.setState methods for PWAs. * PWA: Remove inconsistent return value for setState * Minor cleanup * Fix check-types * Add micro documentation for PWA (get/set)State * Support PWA setState with expression syntax * Fixup types * Review updates and add tests * Fix check-types * Fix empty string return value from getState * Don't limit return type of getState * Fix unit test * Do not emulate event in setState * Really fix unit test

PWA: Expose getState and setState

8f55d2b

Expose shadowDoc.getState and shadowDoc.setState methods for PWAs.

googlebot added the cla: yes label Oct 10, 2019

amp-owners-bot bot requested a review from dreamofabear October 10, 2019 20:47

mattwomple added 5 commits October 10, 2019 17:18

PWA: Remove inconsistent return value for setState

6cd130c

Minor cleanup

237327c

Fix check-types

55c05d3

Merge remote-tracking branch 'origin/master' into patch-3

644328d

Add micro documentation for PWA (get/set)State

ced02e8

mattwomple commented Oct 11, 2019

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mattwomple changed the title ~~[WIP] ✨PWA: Expose getState and setState~~ ✨PWA: Expose amp-bind getState and setState Oct 11, 2019

mattwomple marked this pull request as ready for review October 11, 2019 09:13

mattwomple commented Oct 11, 2019

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extensions/amp-bind/0.1/bind-impl.js Outdated Show resolved Hide resolved

mattwomple added 2 commits October 11, 2019 22:45

Support PWA setState with expression syntax

5d21df4

Fixup types

760c455

mattwomple commented Oct 14, 2019

View reviewed changes

dreamofabear reviewed Oct 14, 2019

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Review updates and add tests

1a1582e

mattwomple added 4 commits October 14, 2019 16:33

Fix check-types

cc55e03

Fix empty string return value from getState

ffb1fed

Don't limit return type of getState

db49313

Fix unit test

d4e78ef

dreamofabear approved these changes Oct 15, 2019

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dvoytenko approved these changes Oct 15, 2019

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mattwomple added 2 commits October 15, 2019 13:16

Do not emulate event in setState

a4b0bb2

Really fix unit test

a30b58e

dreamofabear merged commit 9b45ef8 into ampproject:master Oct 16, 2019

mattwomple deleted the patch-3 branch December 13, 2019 21:34

samouri mentioned this pull request Jan 29, 2020

I2I: "protocol adapters" for client side data massaging. #26474

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✨PWA: Expose amp-bind getState and setState #25011

✨PWA: Expose amp-bind getState and setState #25011

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✨PWA: Expose amp-bind getState and setState #25011

✨PWA: Expose amp-bind getState and setState #25011

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