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Commit d9085810 authored by Robert Knight's avatar Robert Knight
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Refactor `Guest#anchor` 

Rewrite the `Guest#anchor` method to simplify the control flow and
generally make it easier to understand and change. There are no
functional changes for annotations with zero or one entry in the
`target` field (all existing Hypothesis annotations).

There is a functional change to handling of annotations with multiple
targets. Previously `anchor` would try to be smart about only
re-anchoring targets which were not already anchored. In the new
implementation all targets for an annotation are re-anchored. This will have
no effect in practice because the Hypothesis client only supports
creating annotations with a single target and the h backend can only
store a single target per annotation. However the Hypothesis API does
allow for multiple targets per annotation, in line with the W3C Web
Annotations specs in which a single annotation can refer to multiple
parts of a document.

 - Convert `anchor` method to async and replace Promise chains with async/await

 - Replace the logic that removes existing anchors and highlights for an
   annotation with a call to the `detach` method. This required adding
   an internal parameter to `detach` to control whether `anchorsChanged`
   is emitted, so that `anchor` only emits `anchorsChanged` once.

 - Add an explicit error to `Promise.reject` calls in tests so that the
   tests are easier to debug if they fail
parent 3a784bce
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Showing with 76 additions and 141 deletions
src/annotator/guest.js
View file @ d9085810
......@@ -335,83 +335,64 @@ export default class Guest {
}
/**
* Anchor (locate) an annotation's selectors in the document.
* Anchor an annotation's selectors in the document.
*
* _Anchoring_ resolves a set of selectors to a concrete region of the document
* which is then highlighted. The results of anchoring are broadcast to the
* rest of the application via `CrossFrame#sync`.
*
* Any existing anchors associated with `annotation` will be removed before
* re-anchoring the annotation.
*
* @param {AnnotationData} annotation
* @return {Promise<Anchor[]>}
*/
anchor(annotation) {
let anchor;
const root = this.element;
// Anchors for all annotations are in the `anchors` instance property. These
// are anchors for this annotation only. After all the targets have been
// processed these will be appended to the list of anchors known to the
// instance. Anchors hold an annotation, a target of that annotation, a
// document range for that target and an Array of highlights.
const anchors = [];
// The targets that are already anchored. This function consults this to
// determine which targets can be left alone.
const anchoredTargets = [];
// These are the highlights for existing anchors of this annotation with
// targets that have since been removed from the annotation. These will
// be removed by this function.
let deadHighlights = [];
// Initialize the target array.
if (!annotation.target) {
annotation.target = [];
}
async anchor(annotation) {
/**
* Locate the region of the current document that the annotation refers to.
* Resolve an annotation's selectors to a concrete range.
*
* @param {Target} target
* @return {Promise<Anchor>}
*/
const locate = target => {
// Check that the anchor has a TextQuoteSelector -- without a
// TextQuoteSelector we have no basis on which to verify that we have
// reanchored correctly and so we shouldn't even try.
//
// Returning an anchor without a range will result in this annotation being
// treated as an orphan (assuming no other targets anchor).
const locate = async target => {
// Only annotations with an associated quote can currently be anchored.
// This is because the quote is used to verify anchoring with other selector
// types.
if (
!target.selector ||
!target.selector.some(s => s.type === 'TextQuoteSelector')
) {
return Promise.resolve({ annotation, target });
return { annotation, target };
}
// Find a target using the anchoring module.
return this.integration
.anchor(root, target.selector)
.then(range => ({
annotation,
target,
/** @type {Anchor} */
let anchor;
try {
const range = await this.integration.anchor(
this.element,
target.selector
);
// Convert the `Range` to a `TextRange` which can be converted back to
// a `Range` later. The `TextRange` representation allows for highlights
// to be inserted during anchoring other annotations without "breaking"
// this anchor.
range: TextRange.fromRange(range),
}))
.catch(() => ({
annotation,
target,
}));
const textRange = TextRange.fromRange(range);
anchor = { annotation, target, range: textRange };
} catch (err) {
anchor = { annotation, target };
}
return anchor;
};
/**
* Highlight the range for an anchor.
* Highlight the text range that `anchor` refers to.
*
* @param {Anchor} anchor
*/
const highlight = anchor => {
const range = resolveAnchor(anchor);
if (!range) {
return anchor;
return;
}
const highlights = /** @type {AnnotationHighlight[]} */ (highlightRange(
......@@ -421,99 +402,63 @@ export default class Guest {
h._annotation = anchor.annotation;
});
anchor.highlights = highlights;
return anchor;
};
/**
* Inform other parts of Hypothesis (eg. the sidebar and bucket bar) about
* the results of anchoring.
*
* @param {Anchor[]} anchors
*/
const sync = anchors => {
// An annotation is considered to be an orphan if it has at least one
// target with selectors, and all targets with selectors failed to anchor
// (i.e. we didn't find it in the page and thus it has no range).
let hasAnchorableTargets = false;
let hasAnchoredTargets = false;
for (let anchor of anchors) {
if (anchor.target.selector) {
hasAnchorableTargets = true;
if (anchor.range) {
hasAnchoredTargets = true;
break;
}
// Remove existing anchors for this annotation.
this.detach(annotation, false /* notify */);
// Resolve selectors to ranges and insert highlights.
if (!annotation.target) {
annotation.target = [];
}
const anchors = await Promise.all(annotation.target.map(locate));
for (let anchor of anchors) {
highlight(anchor);
}
annotation.$orphan = hasAnchorableTargets && !hasAnchoredTargets;
// Add the anchors for this annotation to instance storage.
this._updateAnchors(this.anchors.concat(anchors));
// Set flag indicating whether anchoring succeeded. For each target,
// anchoring is successful either if there are no selectors (ie. this is a
// Page Note) or we successfully resolved the selectors to a range.
annotation.$orphan =
anchors.length > 0 &&
anchors.every(anchor => anchor.target.selector && !anchor.range);
this._updateAnchors(this.anchors.concat(anchors), true /* notify */);
// Let other frames (eg. the sidebar) know about the new annotation.
this.crossframe.sync([annotation]);
return anchors;
};
// Remove all the anchors for this annotation from the instance storage.
for (anchor of this.anchors.splice(0, this.anchors.length)) {
if (anchor.annotation === annotation) {
// Anchors are valid as long as they still have a range and their target
// is still in the list of targets for this annotation.
if (anchor.range && annotation.target.includes(anchor.target)) {
anchors.push(anchor);
anchoredTargets.push(anchor.target);
} else if (anchor.highlights) {
// These highlights are no longer valid and should be removed.
deadHighlights = deadHighlights.concat(anchor.highlights);
delete anchor.highlights;
delete anchor.range;
}
} else {
// These can be ignored, so push them back onto the new list.
this.anchors.push(anchor);
}
}
// Remove all the highlights that have no corresponding target anymore.
removeHighlights(deadHighlights);
// Anchor any targets of this annotation that are not anchored already.
for (let target of annotation.target) {
if (!anchoredTargets.includes(target)) {
anchor = locate(target).then(highlight);
anchors.push(anchor);
}
}
return Promise.all(anchors).then(sync);
}
/**
* Remove the anchors and associated highlights for an annotation from the document.
*
* @param {AnnotationData} annotation
* @param {boolean} [notify] - For internal use. Whether to emit an `anchorsChanged` notification
*/
detach(annotation) {
detach(annotation, notify = true) {
const anchors = [];
let unhighlight = [];
for (let anchor of this.anchors) {
if (anchor.annotation === annotation) {
unhighlight.push(...(anchor.highlights ?? []));
} else {
if (anchor.annotation !== annotation) {
anchors.push(anchor);
} else if (anchor.highlights) {
removeHighlights(anchor.highlights);
}
}
removeHighlights(unhighlight);
this._updateAnchors(anchors);
this._updateAnchors(anchors, notify);
}
_updateAnchors(anchors) {
/**
* @param {Anchor[]} anchors
* @param {boolean} notify
*/
_updateAnchors(anchors, notify) {
this.anchors = anchors;
if (notify) {
this._emitter.publish('anchorsChanged', this.anchors);
}
}
/**
* Create a new annotation that is associated with the selected region of
......
src/annotator/test/guest-test.js
View file @ d9085810
......@@ -785,7 +785,7 @@ describe('Guest', () => {
};
fakeHTMLIntegration.anchor
.onFirstCall()
.returns(Promise.reject())
.returns(Promise.reject(new Error('Failed to anchor')))
.onSecondCall()
.returns(Promise.resolve(range));
......@@ -801,7 +801,9 @@ describe('Guest', () => {
{ selector: [{ type: 'TextQuoteSelector', exact: 'notinhere' }] },
],
};
fakeHTMLIntegration.anchor.returns(Promise.reject());
fakeHTMLIntegration.anchor.returns(
Promise.reject(new Error('Failed to anchor'))
);
return guest
.anchor(annotation)
......@@ -816,7 +818,9 @@ describe('Guest', () => {
{ selector: [{ type: 'TextQuoteSelector', exact: 'neitherami' }] },
],
};
fakeHTMLIntegration.anchor.returns(Promise.reject());
fakeHTMLIntegration.anchor.returns(
Promise.reject(new Error('Failed to anchor'))
);
return guest
.anchor(annotation)
......@@ -916,20 +920,6 @@ describe('Guest', () => {
assert.calledWith(removeHighlights, highlights);
});
});
it('does not reanchor targets that are already anchored', () => {
const guest = createGuest();
const annotation = {
target: [{ selector: [{ type: 'TextQuoteSelector', exact: 'hello' }] }],
};
fakeHTMLIntegration.anchor.returns(Promise.resolve(range));
return guest.anchor(annotation).then(() =>
guest.anchor(annotation).then(() => {
assert.equal(guest.anchors.length, 1);
assert.calledOnce(fakeHTMLIntegration.anchor);
})
);
});
});
describe('#detach', () => {
......
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