Fable: print AST

[nojaf]

This is a question rather than an actual problem.
I'm currently working on a presentation about Fable and I'd like to show the intermediate steps of how Fable compiles the F# to JS.

I took an easy example

let add a b = a + b

And now I want to show how the Fable AST looks like.
To compare with the Babel AST later on.

I'm also showing in a slide how the FCS AST looks like to illustrate the differences.

[Let
 (false,
  [Binding
     (None,NormalBinding,false,false,[],
      PreXmlDoc
        (Microsoft.FSharp.Compiler.Range+pos,
         Microsoft.FSharp.Compiler.Ast+XmlDocCollector),
      SynValData
        (None,
         SynValInfo
           ([[SynArgInfo ([],false,Some a)];
             [SynArgInfo ([],false,Some b)]],
            SynArgInfo ([],false,None)),None),
      LongIdent
        (LongIdentWithDots ([add],[]),None,None,
         Pats
           [Named
              (Wild Program.fs (2,8--2,9) IsSynthetic=false,a,false,
               None,Program.fs (2,8--2,9) IsSynthetic=false);
            Named
              (Wild Program.fs (2,10--2,11) IsSynthetic=false,b,
               false,None,Program.fs (2,10--2,11) IsSynthetic=false)],
         None,Program.fs (2,4--2,11) IsSynthetic=false),None,

What functions do I use to print the AST?

[alfonsogarciacaro]

We had some rough Fable AST printers but I commented them out because they were causing problems. We could try uncommenting it and see if it works with the quicktest, by uncommenting also this line.

[nojaf]

Thanks Alfonso, I was able to print the Fable AST with those changes.

Entity
  (QuickTest,
   [MemberOrFunctionOrValue
      (val add,[[val a]; [val b]],
       Call
  (None,val op_Addition,[],
   [type Microsoft.FSharp.Core.int; type Microsoft.FSharp.Core.int;
    type Microsoft.FSharp.Core.int],[Value val a; Value val b]))])

As for the Babel AST, I'm guessing I want to print something in Fable2Babel?
I'm expecting the Babel AST is just some json right?

[alfonsogarciacaro]

Ah, great! Sometimes printing the type name gave me some issues but hopefully is fixed now. In the next version I will uncomment those lines (you still have to opt-in the AST printer, so it shouldn't affect anybody else). About the Babel AST, it is converted to JSON before sending it to the JS client yest. Whenever I had to check, I either print it in the JS client (fable-splitter, fable-loader) or right before sending the json over the TCP channel.

[nojaf]

Thanks, changed some code in the rollup-loader and got the babel ast.