refactor: generate idiomatic Motoko for __dfx_asset_path

[ggreif]

Also fail the query when being asked for a non-existing path.

To illustrate, we now generate

            public query func __dfx_asset_path(path: Text): async Text {
              switch path {
                case "index.js" "<the asset contents>";
                case _ {assert false; ""}
              };
            };

[nomeata]

You could actually throw instead of assert, for a better error message.

[ggreif]

AAAAHHHH! Disregard what is below! I shitread the error message :-/

I am a bit shocked because of this (71de8a2) error:

# /private/tmp/nix-build-e2e-tests.drv-0/dfx-e2e-qSJvqkiu/hello/counter_idl.mo-8131923740757337836:11.32-11.55: type error, expression of type
#   Text
# cannot produce expected type
#   Error

Shocked, that throw "shit" : Error. I expected bottom.

[ggreif]

You could actually throw instead of assert, for a better error message.

@nomeata well, that sadly won't work out of the box. Prim.error needs an import, but this is massaged source (method inserted into main actor), and I am uncomfortable also inserting an import __PRIM "mo:prim at the top of the file. Maybe another time.

We are already better, and don't send an empty script to the frontend (failing silently).

[chenyan-dfinity]

LGTM. The whole __dfx_asset_path is temporary, so we don't have to be perfect.

[ggreif]

One way out could be to give __-methods special powers, e.g. automatic importing of "mo:prim".

[chenyan-dfinity]

One way out could be to give __-methods special powers, e.g. automatic importing of "mo:prim".

We don't want to encourage these line of design...

[eftychis]

post merge lgtm -- I second @chenyan-dfinity 's comment that this should stay temporary: hope to break the "nothing more permanent than temporary" saying here.

[nomeata]

well, that sadly won't work out of the box. Prim.error needs an import, but this is massaged source (method inserted into main actor), and I am uncomfortable also inserting an import __PRIM "mo:prim at the top of the file. Maybe another time.

Oh, yes, absolutely not worth the complexity then.