The multi-compiler aspect allows the configuration of multiple compilers on a component. This determines which compiler to apply on a component file using the isFileSupported() compiler API.

  • createCompiler(compilers: Compiler[], options: CompilerOptions) API to support the creation a Multi-compiler instance which can be used in the Env API (the overrideCompiler and getCompiler APIs).
  • Supports the creation of a multi-compiler build tasks.
// create a multi compiler instance.
const compiler = multiCompiler.createCompiler([

// create a multi-compiler build task.
compiler.createTask('MultiCompiler', compiler);

An example of using the multi compiler can be found in the mdx env

Special implementations details


The transpileFile of the multi compiler is taking each one of the files and run it through the compilers. Each compiler get's the output of the previous compiler in the list. The check against isFileSupported are done against the previous compiler output path. for example the ts compiler will compile the code, and change the output file path from .ts to .js, then the next compiler in the list will check isFileSupported with the .js extension. If a compiler in the list does not support a specific file, the file will be passed to the next compiler in the list, as is.


As opposed to the transpile file, the build for all the compiler gets the same context as argument. Which means, by default the compilers will be applied on the original source files, unless they know to read the outputs of the previous compiler from the capsules and use them as a base. The build is running in serial (build of each compiler only starts after the build of previous one finished) this is to be able to support reading the previous compiler output.

pre/post build

The multi compiler will run all the pre/post build functions for any of the compilers that implement them. This tasks will be run in parallel.


The multi compiler will return the distPath returned by the first compiler that support a given file. In case no compilers support a file, it will return join(this.distDir, srcPath);


The multi compiler return true if at least one of the compiler support the file.


The multi compiler will return a string which contain the displayName@version for each one of the compilers, separated by new line. For example