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4a5c980baa
LocalCollection.wrapTransform is idempotent, so it's OK to doubly-wrap them, but it's slightly more efficient to notice that a transform has already been wrapped and not re-wrap it. (One place where we doubly-wrap transforms is in SynchronousCursor, which calls wrapTransform on a transform that probably came from Mongo.Collection, which also wrapped it.) Fixes #3623.
47 lines
1.5 KiB
JavaScript
47 lines
1.5 KiB
JavaScript
// Wrap a transform function to return objects that have the _id field
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// of the untransformed document. This ensures that subsystems such as
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// the observe-sequence package that call `observe` can keep track of
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// the documents identities.
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//
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// - Require that it returns objects
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// - If the return value has an _id field, verify that it matches the
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// original _id field
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// - If the return value doesn't have an _id field, add it back.
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LocalCollection.wrapTransform = function (transform) {
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if (! transform)
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return null;
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// No need to doubly-wrap transforms.
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if (transform.__wrappedTransform__)
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return transform;
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var wrapped = function (doc) {
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if (!_.has(doc, '_id')) {
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// XXX do we ever have a transform on the oplog's collection? because that
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// collection has no _id.
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throw new Error("can only transform documents with _id");
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}
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var id = doc._id;
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// XXX consider making tracker a weak dependency and checking Package.tracker here
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var transformed = Tracker.nonreactive(function () {
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return transform(doc);
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});
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if (!isPlainObject(transformed)) {
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throw new Error("transform must return object");
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}
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if (_.has(transformed, '_id')) {
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if (!EJSON.equals(transformed._id, id)) {
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throw new Error("transformed document can't have different _id");
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}
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} else {
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transformed._id = id;
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}
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return transformed;
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};
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wrapped.__wrappedTransform__ = true;
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return wrapped;
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};
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