How to ignore jsDoc while generating code using printNode function from Typescript compiler api?

Question

Typescript compiler API allows us to process abstract syntax tree (AST) and generate source code. We can do it by creating a printer object and using printNode function

const printer = ts.createPrinter({ newLine: ts.NewLineKind.LineFeed });
printer.printNode(ts.EmitHint.Unspecified, node, sourceFile))

The problem I'm facing is that my AST contains lots of jsDoc in various places and I want to ignore them and print code without comments. Is there any way to do it without manually traversing the AST and removing jsDoc objects?

David Sherret · Accepted Answer · 2021-12-15 17:24:43Z

1

Based on looking at the printer code (see shouldWriteComment and follow the code out of there) it doesn't seem possible out of the box.

One way you could hack this is to set the positions of all declarations that have jsdocs to be -1 or node.pos = node.getStart(sourceFile):

> ts.createPrinter({}).printNode(node, sourceFile)
'/** Test */\r\nfunction test() {\r\n    test;\r\n}\r\n'
> node.pos = -1
> ts.createPrinter({}).printNode(node, sourceFile)
'function test() {\r\n    test;\r\n}\r\n'

answered Dec 15, 2021 at 17:24

David Sherret

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2 Comments

Arkadiusz Kałkus Over a year ago

Thank you for the answer David. Moving code up would help with comments above declarations of types but not above properties if I understand correctly. In the meantime - by the way - I found that removing jsDoc properties from AST doesn't affect output, because it seems to be generated from text property, not from AST, surprisingly...

David Sherret Over a year ago

Yeah, the jsdocs are emitted from the source file text based on the position of the node. The ts compiler is designed for whatever works best for compiling the code so I guess they decided to do that because it left the jsdoc text the same more reliably. Also, doing -1 won't move the code up, but will just cause the printer to not emit any comments for that node. -1 is what's used by default for the pos for nodes created with factory functions.

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