planning

node_modules/@mapbox/mapbox-gl-style-spec/expression/definitions/var.js

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+// @flow
+
+import type {Type} from '../types.js';
+import type {Expression} from '../expression.js';
+import type ParsingContext from '../parsing_context.js';
+import type EvaluationContext  from '../evaluation_context.js';
+
+class Var implements Expression {
+    type: Type;
+    name: string;
+    boundExpression: Expression;
+
+    constructor(name: string, boundExpression: Expression) {
+        this.type = boundExpression.type;
+        this.name = name;
+        this.boundExpression = boundExpression;
+    }
+
+    static parse(args: $ReadOnlyArray<mixed>, context: ParsingContext): void | Var {
+        if (args.length !== 2 || typeof args[1] !== 'string')
+            return context.error(`'var' expression requires exactly one string literal argument.`);
+
+        const name = args[1];
+        if (!context.scope.has(name)) {
+            return context.error(`Unknown variable "${name}". Make sure "${name}" has been bound in an enclosing "let" expression before using it.`, 1);
+        }
+
+        return new Var(name, context.scope.get(name));
+    }
+
+    evaluate(ctx: EvaluationContext): any {
+        return this.boundExpression.evaluate(ctx);
+    }
+
+    eachChild() {}
+
+    outputDefined(): boolean {
+        return false;
+    }
+
+    serialize(): Array<string> {
+        return ["var", this.name];
+    }
+}
+
+export default Var;