Function traverseAst

packages/jest-snapshot/src/utils.ts:375–430

(
  snapshots: Array<InlineSnapshot>,
  ast: File | Program,
  snapshotMatcherNames: Array<string>,
)

export const groupSnapshotsByFile = groupSnapshotsBy(({frame: {file}}) => file);

const traverseAst = (
  snapshots: Array<InlineSnapshot>,
  ast: File | Program,
  snapshotMatcherNames: Array<string>,
) => {
  const groupedSnapshots = groupSnapshotsByFrame(snapshots);
  const remainingSnapshots = new Set(snapshots.map(({snapshot}) => snapshot));

  traverseFast(ast, (node: Node) => {
    if (node.type !== 'CallExpression') return;

    const {arguments: args, callee} = node;
    if (
      callee.type !== 'MemberExpression' ||
      callee.property.type !== 'Identifier' ||
      callee.property.loc == null
    ) {
      return;
    }
    const {line, column} = callee.property.loc.start;
    const snapshotsForFrame = groupedSnapshots[`${line}:${column}`];
    if (!snapshotsForFrame) {
      return;
    }
    if (snapshotsForFrame.length > 1) {
      throw new Error(
        'Jest: Multiple inline snapshots for the same call are not supported.',
      );
    }
    const inlineSnapshot = snapshotsForFrame[0];
    inlineSnapshot.node = node;

    snapshotMatcherNames.push(callee.property.name);

    const snapshotIndex = args.findIndex(
      ({type}) => type === 'TemplateLiteral' || type === 'StringLiteral',
    );

    const {snapshot} = inlineSnapshot;
    remainingSnapshots.delete(snapshot);
    const replacementNode = templateLiteral(
      [templateElement({raw: escapeBacktickString(snapshot)})],
      [],
    );

    if (snapshotIndex === -1) {
      args.push(replacementNode);
    } else {
      args[snapshotIndex] = replacementNode;
    }
  });

  if (remainingSnapshots.size > 0) {
    throw new Error("Jest: Couldn't locate all inline snapshots.");
  }
};