Developer builds tool to map Angular accessibility violations to exact template source lines

A developer identified a major usability gap in accessibility scanning tools, which report violations using rendered DOM selectors that are difficult to trace back to Angular component template files. To solve this, they leveraged Angular's own compiler API, parseTemplate, which provides AST nodes with precise byte offsets, line numbers, and column positions for every element in a template. The approach inserts debug attributes directly into template source text using back-to-front offset edits, avoiding the need to regenerate files from the AST. A key challenge was correctly traversing Angular's control flow blocks — such as @if, @for, and @defer — which store child nodes in non-standard properties like branches, groups, and slots rather than a simple children array. The developer also found that instanceof checks for element nodes are unreliable when multiple versions of @angular/compiler are installed, requiring structural duck-typing instead.