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New Language Intake

This document outlines the process to be followed when introducing a new jsii target language, including an estimated timeline (the exact timeline may vary significantly depending on the specifics of the language being added).

The estimated total duration for the process is 4 to 6 months.


⏰ Estimated Duration: 2 weeks

The first step is to study the jsii specification, as well as existing language implementations, in order to have the knowledge necessary to write a new language support proposal RFC. The RFC document produced will evolve and be polished as development of the new language support progresses, but the following elements must be present before any implementation begins:

  • Identification of the language's standard package repository
  • Proposal for the binding's configuration block
  • Sample API representations in the proposed language
  • In particular, any element from the jsii type model that does not naturally map into the proposed new language needs to be represented
  • Where several options exist, links to prior art are instrumental to validate the direction chosen
  • Toolchain and platform requirements

Code Generation (jsii-pacmak)

⏰ Estimated Duration: 4 to 6 weeks

The necessary code must be added to [jsii-pacmak] in order to map the jsii assembly's declared types into the proposed language. While this code ought to leverage the new language's host runtime library, we begin with writing the code generator in order to ensure the appropriate developer experience is achieved in the new language before writing the back-end components.

Code generators are authored in TypeScript.

The necessary reserved words need to be registered in the jsii compiler, so that warnings are produced when identifiers are used in TypeScript code that require slugification or escaping in the target language (and will hence cause a degraded developer experience).

Runtime Library

⏰ Estimated Duration: 4 to 6 weeks

Now that the appropriate developer experience has been identified, the host runtime library supporting the generated code can be written. This component must be written in the new language.


A reference architecture for host runtime libraries is to be developed, in order to ensure consistent naming and behavior across all the runtimes, reducing the cost of maintaining many of those.

Building & Packaging

⏰ Estimated Duration: 2 weeks

Once code is generated and it has a host runtime library to rely on, [jsii-pacmak] needs to receive the additional logic required to compile and package the generated libraries as required, producing ready-to-publish artifacts.

The necessary toolchain needs to be added to the [] Docker image, so that jsii customers can rely on this to build artifacts for any of the supported languages.

In addition to this, standardized Amazon CodePipeline actions need to be developed in order to support publishing to the relevant idiomatic package managers.

Compliance Tests

⏰ Estimated Duration: 6 weeks

The full standard compliance suite must be implemented for the new language. Leveraging the new code generator, host runtime library and compilation logic, the tests demonstrate that the new library behaves consistently with all other language bindings.

While it is possible to declare developer preview on a new language before all the tests pass, full compliance is a pre-requisite to declaring general availability of the new language.


⏰ Estimated Duration: 1 week

The necessary documentation needs to be provided to support customers who want to onboard the new language. This also includes updating [jsii-config] with support for the new languages' configuration block.

Developer Preview

⏰ Recommended Duration: 4 to 8 weeks

It is possible to declare Developer Preview for a new language support as soon as the code generation and host runtime library are mature enough to be useful, and cover the majority of use-cases. While certain edge-cases may still be uncovered at the beginning of Developer Preview, a clear plan should exist that ensures a path exists to address any known gaps. It is required to have implemented most of the standard compliance suite prior to declaring Developer Preview.

During the Developer Preview phase, user experience studies should be conducted to validate assumptions made during the code generator's design. If any significant change is dictated by the results of the user experience studies, fluback studies should be performed in order to confirm that the desired impact has been achieved.


A standard set of user experience study tasks will be developed, ensuring the learnings from previous experiences is factored into subsequent studies conducted.

Finally, it is essential to give time to the community to use and vet the new language support prior to considering General Availability. A minimum of a full month without a major bug reported is advised. During this period, intentional hands-on usage of the product msut be performed by engineers familiar with the new language as well as engineers unfamilar with it. This ensures the new experience is considered holistically, in a manner unbiased by knowledge of the implementation.

General Availability

Once the new language support has been Developer Preview for long enough and the engineers involved have gained confidence that the API is stable, covers all known use-cases reliably, and behaves consistently with other Generally Available languages, the new support can be considered for General Availability.