function expandStringConcat()

in packages/babel-plugin-fbt/src/FbtUtil.js [465:519]

• 40 lines of code
• 11 McCabe index (conditional complexity)

function expandStringConcat(
  moduleName: string,
  node: BabelNode,
): BabelNodeStringLiteral | BabelNodeJSXText {
  if (isBinaryExpression(node)) {
    if (node.operator !== '+') {
      throw errorAt(
        node,
        `Expected concatenation operator (+) but got ${node.operator}`,
      );
    }
    return stringLiteral(
      expandStringConcat(moduleName, node.left).value +
        expandStringConcat(moduleName, node.right).value,
    );
  } else if (isStringLiteral(node)) {
    return node;
  } else if (isJSXText(node)) {
    return node;
  } else if (isTemplateLiteral(node)) {
    let string = '';
    const expressions = node.expressions;

    let index = 0;
    for (const elem of node.quasis) {
      if (elem.value.cooked) {
        string += elem.value.cooked;
      }

      if (index < expressions.length) {
        const expr = expressions[index++];
        // fbt.param expressions are already transformed to StringLiteral
        if (!isStringLiteral(expr)) {
          throw errorAt(
            node,
            `${moduleName} template placeholders only accept params wrapped in ` +
              `${moduleName}.param. Expected StringLiteral got ${expr.type}`,
          );
        }
        string += expr.value;
      }
    }

    return stringLiteral(string);
  }

  throw errorAt(
    node,
    `${moduleName} only accepts plain strings with params wrapped in ${moduleName}.param(...). ` +
      `See the docs at https://facebook.github.io/fbt/ for more info. ` +
      `Expected StringLiteral, TemplateLiteral, or concatenation; ` +
      // $FlowExpectedError This BabelNode is unsupported so it may not even have a type property
      `got "${node.type}"`,
  );
}