Rewrite TypeScript imports at compile time

compile.ts

import ts from 'typescript'

const unpackImportPath = (node: ts.ImportDeclaration): string => {
  const moduleSpecifier = node.moduleSpecifier as ts.StringLiteral
  return moduleSpecifier.text
}

const transformImport = (
  factory: ts.NodeFactory,
  node: ts.ImportDeclaration,
): ts.ImportDeclaration => {
  return factory.updateImportDeclaration(
    node,
    node.modifiers,
    node.importClause,
    factory.createStringLiteral('NEW PATH GOES HERE'),
    undefined,
  )
}

const transformer: ts.TransformerFactory<ts.SourceFile> = (context) => {
  const visitor: ts.Visitor = (node) => {
    if (ts.isImportDeclaration(node)) {
      return transformImport(context.factory, node)
    }

    return ts.visitEachChild(node, visitor, context)
  }

  return (sourceFile) => {
    return ts.visitNode(sourceFile, visitor)
  }
}

// using ts.transpileModule
const {
  outputText,
  diagnostics,
 } = ts.transpileModule(`TS SOURCE CODE`, {
  transformers: { after: [ transformer ] },
  compilerOptions: {
    // ...
  },
})

// using ts.createProgram
const program = ts.createProgram(
  [ FILE_PATHS_GO_HERE ],
  {
    // compilerOptions...
  },
)

program.emit(
  undefined,
  undefined,
  undefined,
  undefined,
  {
    after: [ transformer ],
  },
)