| 1 | import {Operator} from 'vega-dataflow';
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| 2 | import {inherits, key} from 'vega-util';
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| 3 |
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| 4 | /**
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| 5 | * Generates a key function.
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| 6 | * @constructor
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| 7 | * @param {object} params - The parameters for this operator.
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| 8 | * @param {Array<string>} params.fields - The field name(s) for the key function.
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| 9 | * @param {boolean} params.flat - A boolean flag indicating if the field names
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| 10 | * should be treated as flat property names, side-stepping nested field
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| 11 | * lookups normally indicated by dot or bracket notation.
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| 12 | */
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| 13 | export default function Key(params) {
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| 14 | Operator.call(this, null, update, params);
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| 15 | }
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| 16 |
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| 17 | inherits(Key, Operator);
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| 18 |
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| 19 | function update(_) {
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| 20 | return (this.value && !_.modified()) ? this.value : key(_.fields, _.flat);
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| 21 | }
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