packages/babel-template/src/populate.js
// @flow
import * as t from "@babel/types";
import type { TemplateReplacements } from "./options";
import type { Metadata, Placeholder } from "./parse";
export default function populatePlaceholders(
metadata: Metadata,
replacements: TemplateReplacements,
): BabelNodeFile {
const ast = t.cloneNode(metadata.ast);
if (replacements) {
metadata.placeholders.forEach(placeholder => {
if (
!Object.prototype.hasOwnProperty.call(replacements, placeholder.name)
) {
const placeholderName = placeholder.name;
throw new Error(
`Error: No substitution given for "${placeholderName}". If this is not meant to be a
placeholder you may want to consider passing one of the following options to @babel/template:
- { placeholderPattern: false, placeholderWhitelist: new Set(['${placeholderName}'])}
- { placeholderPattern: /^${placeholderName}$/ }`,
);
}
});
Object.keys(replacements).forEach(key => {
if (!metadata.placeholderNames.has(key)) {
throw new Error(`Unknown substitution "${key}" given`);
}
});
}
// Process in reverse order so AST mutation doesn't change indices that
// will be needed for later calls to `placeholder.resolve()`.
metadata.placeholders
.slice()
.reverse()
.forEach(placeholder => {
try {
applyReplacement(
placeholder,
ast,
(replacements && replacements[placeholder.name]) || null,
);
} catch (e) {
e.message = `@babel/template placeholder "${placeholder.name}": ${e.message}`;
throw e;
}
});
return ast;
}
function applyReplacement(
placeholder: Placeholder,
ast: BabelNodeFile,
replacement: any,
) {
// Track inserted nodes and clone them if they are inserted more than
// once to avoid injecting the same node multiple times.
if (placeholder.isDuplicate) {
if (Array.isArray(replacement)) {
replacement = replacement.map(node => t.cloneNode(node));
} else if (typeof replacement === "object") {
replacement = t.cloneNode(replacement);
}
}
const { parent, key, index } = placeholder.resolve(ast);
if (placeholder.type === "string") {
if (typeof replacement === "string") {
replacement = t.stringLiteral(replacement);
}
if (!replacement || !t.isStringLiteral(replacement)) {
throw new Error("Expected string substitution");
}
} else if (placeholder.type === "statement") {
if (index === undefined) {
if (!replacement) {
replacement = t.emptyStatement();
} else if (Array.isArray(replacement)) {
replacement = t.blockStatement(replacement);
} else if (typeof replacement === "string") {
replacement = t.expressionStatement(t.identifier(replacement));
} else if (!t.isStatement(replacement)) {
replacement = t.expressionStatement((replacement: any));
}
} else {
if (replacement && !Array.isArray(replacement)) {
if (typeof replacement === "string") {
replacement = t.identifier(replacement);
}
if (!t.isStatement(replacement)) {
replacement = t.expressionStatement((replacement: any));
}
}
}
} else if (placeholder.type === "param") {
if (typeof replacement === "string") {
replacement = t.identifier(replacement);
}
if (index === undefined) throw new Error("Assertion failure.");
} else {
if (typeof replacement === "string") {
replacement = t.identifier(replacement);
}
if (Array.isArray(replacement)) {
throw new Error("Cannot replace single expression with an array.");
}
}
if (index === undefined) {
t.validate(parent, key, replacement);
(parent: any)[key] = replacement;
} else {
const items: Array<BabelNode> = (parent: any)[key].slice();
if (placeholder.type === "statement" || placeholder.type === "param") {
if (replacement == null) {
items.splice(index, 1);
} else if (Array.isArray(replacement)) {
items.splice(index, 1, ...replacement);
} else {
items[index] = replacement;
}
} else {
items[index] = replacement;
}
t.validate(parent, key, items);
(parent: any)[key] = items;
}
}