Function insertImport

packages/schematics/angular/utility/ast-utils.ts:23–91

(
  source: ts.SourceFile,
  fileToEdit: string,
  symbolName: string,
  fileName: string,
  isDefault = false,
  alias?: string,
)

 * @return Change
 */
export function insertImport(
  source: ts.SourceFile,
  fileToEdit: string,
  symbolName: string,
  fileName: string,
  isDefault = false,
  alias?: string,
): Change {
  const rootNode = source;
  const allImports = findNodes(rootNode, ts.isImportDeclaration);
  const importExpression = alias ? `${symbolName} as ${alias}` : symbolName;

  // get nodes that map to import statements from the file fileName
  const relevantImports = allImports.filter((node) => {
    return ts.isStringLiteralLike(node.moduleSpecifier) && node.moduleSpecifier.text === fileName;
  });

  if (relevantImports.length > 0) {
    const hasNamespaceImport = relevantImports.some((node) => {
      return node.importClause?.namedBindings?.kind === ts.SyntaxKind.NamespaceImport;
    });

    // if imports * from fileName, don't add symbolName
    if (hasNamespaceImport) {
      return new NoopChange();
    }

    const imports = relevantImports.flatMap((node) => {
      return node.importClause?.namedBindings && ts.isNamedImports(node.importClause.namedBindings)
        ? node.importClause.namedBindings.elements
        : [];
    });

    // insert import if it's not there
    if (!imports.some((node) => (node.propertyName || node.name).text === symbolName)) {
      const fallbackPos =
        findNodes(relevantImports[0], ts.SyntaxKind.CloseBraceToken)[0].getStart() ||
        findNodes(relevantImports[0], ts.SyntaxKind.FromKeyword)[0].getStart();

      return insertAfterLastOccurrence(imports, `, ${importExpression}`, fileToEdit, fallbackPos);
    }

    return new NoopChange();
  }

  // no such import declaration exists
  const useStrict = findNodes(rootNode, ts.isStringLiteral).filter((n) => n.text === 'use strict');
  let fallbackPos = 0;
  if (useStrict.length > 0) {
    fallbackPos = useStrict[0].end;
  }
  const open = isDefault ? '' : '{ ';
  const close = isDefault ? '' : ' }';
  const eol = getEOL(rootNode.getText());
  // if there are no imports or 'use strict' statement, insert import at beginning of file
  const insertAtBeginning = allImports.length === 0 && useStrict.length === 0;
  const separator = insertAtBeginning ? '' : `;${eol}`;
  const toInsert =