packages/babel-types/src/modifications/flow/removeTypeDuplicates.js
// @flow
import {
isAnyTypeAnnotation,
isGenericTypeAnnotation,
isUnionTypeAnnotation,
isFlowBaseAnnotation,
} from "../../validators/generated";
/**
* Dedupe type annotations.
*/
export default function removeTypeDuplicates(
nodes: Array<Object>,
): Array<Object> {
const generics = {};
const bases = {};
// store union type groups to circular references
const typeGroups = [];
const types = [];
for (let i = 0; i < nodes.length; i++) {
const node = nodes[i];
if (!node) continue;
// detect duplicates
if (types.indexOf(node) >= 0) {
continue;
}
// this type matches anything
if (isAnyTypeAnnotation(node)) {
return [node];
}
if (isFlowBaseAnnotation(node)) {
bases[node.type] = node;
continue;
}
if (isUnionTypeAnnotation(node)) {
if (typeGroups.indexOf(node.types) < 0) {
nodes = nodes.concat(node.types);
typeGroups.push(node.types);
}
continue;
}
// find a matching generic type and merge and deduplicate the type parameters
if (isGenericTypeAnnotation(node)) {
const name = node.id.name;
if (generics[name]) {
let existing = generics[name];
if (existing.typeParameters) {
if (node.typeParameters) {
existing.typeParameters.params = removeTypeDuplicates(
existing.typeParameters.params.concat(node.typeParameters.params),
);
}
} else {
existing = node.typeParameters;
}
} else {
generics[name] = node;
}
continue;
}
types.push(node);
}
// add back in bases
for (const type of Object.keys(bases)) {
types.push(bases[type]);
}
// add back in generics
for (const name of Object.keys(generics)) {
types.push(generics[name]);
}
return types;
}