nodejs/doc/contributing/adding-new-napi-api.md

# Contributing a new API to Node-API

Node-API is the next-generation ABI-stable API for native addons.
While improving the API surface is encouraged and welcomed, the following are
a set of principles and guidelines to keep in mind while adding a new
Node-API.

* A new API **must** adhere to Node-API API shape and spirit.
  * **Must** be a C API.
  * **Must** not throw exceptions.
  * **Must** return `napi_status`.
  * **Should** consume `napi_env`.
  * **Must** operate only on primitive data types, pointers to primitive
    data types or opaque handles.
  * **Must** be a necessary API and not a nice to have. Convenience APIs
    belong in node-addon-api.
  * **Must** not change the signature of an existing Node-API API or break
    ABI compatibility with other versions of Node.js.
* New API **should** be agnostic towards the underlying JavaScript VM.
* New API PRs **must** have a corresponding documentation update.
* New API PRs **must** be tagged as **node-api**.
* There **must** be at least one test case showing how to use the API.
* There **should** be at least one test case per interesting use of the API.
* There **should** be a sample provided that operates in a realistic way
  (operating how a real addon would be written).
* A new API **should** be discussed at the Node-API team meeting.
* A new API addition **must** be signed off by at least two members of
  the Node-API team.
* A new API addition **should** be simultaneously implemented in at least
  one other VM implementation of Node.js.
* A new API **must** be considered experimental for at least one minor
  version release of Node.js before it can be considered for promotion out
  of experimental.
  * Experimental APIs **must** be documented as such.
  * Experimental APIs **must** require an explicit compile-time flag
    (`#define`) to be set to opt-in.
  * A feature flag of the form `NODE_API_EXPERIMENTAL_HAS_<FEATURE>` **must**
    be added with each experimental feature in order to allow code to
    distinguish between experimental features as present in one version of
    Node.js versus another.
  * Experimental APIs **must** be considered for backport.
  * Experimental status exit criteria **must** involve at least the
    following:
    * A new PR **must** be opened in `nodejs/node` to remove experimental
      status. This PR **must** be tagged as **node-api** and **semver-minor**.
    * Exiting an API from experimental **must** be signed off by the team.
    * If a backport is merited, an API **must** have a down-level
      implementation.
    * The API **should** be used by a published real-world module. Use of
      the API by a real-world published module will contribute favorably
      to the decision to take an API out of experimental status.
    * The API **must** be implemented in a Node.js implementation with an
      alternate VM.

Since the adoption of the policy whereby moving to a later version of Node-API
from an earlier version may entail rework of existing code, it is possible to
introduce modifications to already-released Node-APIs, as long as the
modifications affect neither the ABI nor the API of earlier versions. Such
modifications **must** be accompanied by an opt-out flag. This provides add-on
maintainers who take advantage of the initial compile-time flag to track
impending changes to Node-API with

* a quick fix to the breakage caused,
* a notification that such breakage is impending, and thus
* a buffer to adoption above and beyond the one provided by the initial
  compile-time flag.