Insert arbitrary text and modify NodeArrays in the TypeScript compiler API

Question

// Input
class Foo {
    templateString = 'some value';
}

// Output
import __LIB__ from '@scope/lib/path/to/lib';

class Foo {
    templateString = (function compiledTemplate(deps) {
        // ...
        return result;
    })({lib: __LIB__});
}

In fact, I have two questions:

How to create AST-fragment from string?
How to add import?

P.S. I tried various methods createSourceFile and ts.createImportDeclaration, but they all lead to this or that error: [

Have you tried just creating an Identifier with the appropriate text for the replacement node? In other words: createIdentifier(`(function compiledTemplate(deps) { /*...*/ }`). — Daniel Rosenwasser
– Daniel Rosenwasser, Commented Jun 5, 2017 at 7:43

Daniel Rosenwasser · Accepted Answer · 2017-06-05 16:41:08Z

5

To add in arbitrary text, the best way I know of is to use createIdentifier with the string you want to insert.

To add in an import statement, remember that you're updating the tree without mutating the original.

The ts.visitEachChild API takes a nodesVisitor parameter which specially operates on NodeArrays. Usually, if you don't pass a nodesVisitor in, it will operate on each Node in the NodeArray using the first callback you pass for the visitor parameter, but here you specially want to operate on the full node array.

In your case, you're interested in a SourceFile's statements (which is a NodeArray<Statement>. You can create the import with createImportDeclaration, and update the SourceFile by passing in a nodesVisitor like the following:

function addImport(statements: ts.NodeArray<ts.Statement>) {
    const importStatement = ts.createImportStatement(/*...*/);
    return ts.createNodeArray([importStatement, ...statements]);
}

visitEachChild(
    sourceFile,
    /*replace this with something that controls traversal*/ x => x,
    context, 
    addImport);

edited Jun 5, 2017 at 16:41

answered Jun 5, 2017 at 8:11

Daniel Rosenwasser

24.2k14 gold badges54 silver badges66 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

RubaXa Over a year ago

Alas, don't work: gist.github.com/RubaXa/…

Daniel Rosenwasser Over a year ago

Check out the example I gave for how to create a new node and how to call visitEachChild.

RubaXa Over a year ago

Happened, but still does not work correctly: github.com/RubaXa/typescript-api-questions/tree/master/…

Collectives™ on Stack Overflow

Insert arbitrary text and modify NodeArrays in the TypeScript compiler API

1 Answer 1

3 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

3 Comments

Your Answer

Sign up or log in

Post as a guest

Related