feat: add plot/vega/value/field-descriptor

lib/node_modules/@stdlib/plot/vega/value/field-descriptor/examples/index.js

@@ -0,0 +1,28 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2026 The Stdlib Authors.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+*    http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+'use strict';
+
+var FieldDescriptor = require( './../lib' );
+
+var descriptor = new FieldDescriptor({
+	'parent': new FieldDescriptor({
+		'datum': 'f'
+	})
+});
+console.log( descriptor.toJSON() );

lib/node_modules/@stdlib/plot/vega/value/field-descriptor/lib/change_event.js

@@ -0,0 +1,41 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2026 The Stdlib Authors.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+*    http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+'use strict';
+
+// MAIN //
+
+/**
+* Returns a new change event object.
+*
+* @private
+* @param {string} property - property name
+* @returns {Object} event object
+*/
+function event( property ) { // eslint-disable-line stdlib/no-redeclare
+	return {
+		'type': 'update',
+		'source': 'value',
+		'property': property
+	};
+}
+
+
+// EXPORTS //
+
+module.exports = event;

lib/node_modules/@stdlib/plot/vega/value/field-descriptor/lib/datum/get.js

@@ -0,0 +1,43 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2026 The Stdlib Authors.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+*    http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+/* eslint-disable no-invalid-this */
+
+'use strict';
+
+// MODULES //
+
+var prop = require( './properties.js' );
+
+
+// MAIN //
+
+/**
+* Returns the field lookup on the current data object.
+*
+* @private
+* @returns {(string|FieldDescriptor|void)} field lookup
+*/
+function get() {
+	return this[ prop.private ];
+}
+
+
+// EXPORTS //
+
+module.exports = get;

lib/node_modules/@stdlib/plot/vega/value/field-descriptor/lib/datum/properties.js

@@ -0,0 +1,33 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2026 The Stdlib Authors.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+*    http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+'use strict';
+
+// MODULES //
+
+var property2object = require( '@stdlib/plot/vega/base/property2object' );
+
+
+// MAIN //
+
+var obj = property2object( 'datum' );
+
+
+// EXPORTS //
+
+module.exports = obj;

lib/node_modules/@stdlib/plot/vega/value/field-descriptor/lib/datum/set.js

@@ -0,0 +1,66 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2026 The Stdlib Authors.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+*    http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+/* eslint-disable no-invalid-this */
+
+'use strict';
+
+// MODULES //
+
+var logger = require( 'debug' );
+var isString = require( '@stdlib/assert/is-string' ).isPrimitive;
+var isUndefined = require( '@stdlib/assert/is-undefined' );
+var format = require( '@stdlib/string/format' );
+var changeEvent = require( './../change_event.js' );
+var prop = require( './properties.js' );
+
+
+// VARIABLES //
+
+var debug = logger( 'vega:value:field-descriptor:set:'+prop.name );
+
+
+// MAIN //
+
+/**
+* Sets the field lookup on the current data object.
+*
+* ## Notes
+*
+* -   Providing `undefined` "unsets" the configured value.
+*
+* @private
+* @param {(string|FieldDescriptor|void)} value - input value
+* @throws {TypeError} must be a string or a field descriptor instance
+* @returns {void}
+*/
+function set( value ) {
+	if ( !isString( value ) && !isUndefined( value ) && !this._isFieldDescriptor( value ) ) {
+		throw new TypeError( format( 'invalid assignment. `%s` must be a string or a field descriptor instance. Value: `%s`.', prop.name, value ) );
+	}
+	if ( value !== this[ prop.private ] ) {
+		debug( 'Current value: %s. New value: %s.', JSON.stringify( this[ prop.private ] ), JSON.stringify( value ) );
+		this[ prop.private ] = value;
+		this.emit( 'change', changeEvent( prop.name ) );
+	}
+}
+
+
+// EXPORTS //
+
+module.exports = set;

lib/node_modules/@stdlib/plot/vega/value/field-descriptor/lib/defaults.js

@@ -0,0 +1,43 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2026 The Stdlib Authors.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+*    http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+'use strict';
+
+// MAIN //
+
+/**
+* Returns defaults.
+*
+* @private
+* @returns {Object} default options
+*
+* @example
+* var o = defaults();
+* // returns {...}
+*/
+function defaults() {
+	return {
+		// Nesting level for `group` and `parent` references:
+		'level': 1
+	};
+}
+
+
+// EXPORTS //
+
+module.exports = defaults;

lib/node_modules/@stdlib/plot/vega/value/field-descriptor/lib/group/get.js

@@ -0,0 +1,43 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2026 The Stdlib Authors.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+*    http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+/* eslint-disable no-invalid-this */
+
+'use strict';
+
+// MODULES //
+
+var prop = require( './properties.js' );
+
+
+// MAIN //
+
+/**
+* Returns the field lookup on the enclosing group mark instance.
+*
+* @private
+* @returns {(string|FieldDescriptor|void)} field lookup
+*/
+function get() {
+	return this[ prop.private ];
+}
+
+
+// EXPORTS //
+
+module.exports = get;

lib/node_modules/@stdlib/plot/vega/value/field-descriptor/lib/group/properties.js

@@ -0,0 +1,33 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2026 The Stdlib Authors.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+*    http://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+
+'use strict';
+
+// MODULES //
+
+var property2object = require( '@stdlib/plot/vega/base/property2object' );
+
+
+// MAIN //
+
+var obj = property2object( 'group' );
+
+
+// EXPORTS //
+
+module.exports = obj;