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doc: add note about forwarding stream options
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It is a common and unfortunate pattern to simply just forward
any and all options into the base constructor without taking
into account whether these options might conflict with basic
stream assumptions.

PR-URL: #29857
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
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ronag authored and targos committed Oct 14, 2019
1 parent fc53345 commit cbd1251
Showing 1 changed file with 13 additions and 2 deletions.
15 changes: 13 additions & 2 deletions doc/api/stream.md
Original file line number Diff line number Diff line change
Expand Up @@ -1641,13 +1641,24 @@ parent class constructor:
const { Writable } = require('stream');

class MyWritable extends Writable {
constructor(options) {
super(options);
constructor({ highWaterMark, ...options }) {
super({
highWaterMark,
autoDestroy: true,
emitClose: true
});
// ...
}
}
```

When extending streams, it is important to keep in mind what options the user
can and should provide before forwarding these to the base constructor. For
example, if the implementation makes assumptions in regard to e.g. the
`autoDestroy` and `emitClose` options, it becomes important to not allow the
user to override these. It is therefore recommended to be explicit about what
options are forwarded instead of implicitly forwarding all options.

The new stream class must then implement one or more specific methods, depending
on the type of stream being created, as detailed in the chart below:

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