Rabee Rabee - 3 years ago 447
TypeScript Question

Is it possible to get comments as nodes in the AST using the typescript compiler API?

I would like to extract the comments from a typescript source file, preferably with their line numbers. I tried doing it like this:

var program = ts.createProgram(files, {
target: ts.ScriptTarget.ES5, module: ts.ModuleKind.CommonJS, removeComments: false
ts.forEachChild(sourceFile, visit);

function visit(node) {
if (node.kind == ts.SyntaxKind.SingleLineCommentTrivia){
//print something
ts.forEachChild(node, visit);

In fact, when I printed all the nodes' text, I could see that the comments were discarded entirely. The input source code I used for testing is:

//test comment
declare namespace myLib {
//another comment
function makeGreeting(s: string): string;
let numberOfGreetings: number;

Answer Source

It's not possible to get comments as nodes but it is still possible to get comments from the source file. The function to use is getLeadingCommentRanges(text: string, pos: number).

I used it like this:

for(var sourceFile of program.getSourceFiles()){
        ts.forEachChild(sourceFile, visit);

function visit(node: ts.Node){
    let comments = ts.getLeadingCommentRanges(sourceFile.getText(), node.getFullStart();
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