Add which helpers to Script module.

examples/end-to-end/script/src/Which.elm

@@ -0,0 +1,16 @@
+module Which exposing (run)
+
+import BackendTask exposing (BackendTask)
+import Pages.Script as Script exposing (Script, doThen, sleep)
+import Pages.Script.Spinner as Spinner
+
+
+run : Script
+run =
+    Script.withoutCliOptions
+        (Script.expectWhich "elm"
+            |> BackendTask.andThen
+                (\elmPath ->
+                    Script.log elmPath
+                )
+        )

generator/src/render.js

@@ -14,6 +14,7 @@ import * as fs from "node:fs";
 import * as crypto from "node:crypto";
 import { restoreColorSafe } from "./error-formatter.js";
 import { Spinnies } from './spinnies/index.js'
+import { default as which } from "which";
 
 const spinnies = new Spinnies();
 
@@ -504,6 +505,8 @@ async function runInternalJob(
       return [requestHash, await runWriteFileJob(requestToPerform)];
     } else if (requestToPerform.url === "elm-pages-internal://sleep") {
       return [requestHash, await runSleep(requestToPerform)];
+    } else if (requestToPerform.url === "elm-pages-internal://which") {
+      return [requestHash, await runWhich(requestToPerform)];
     } else if (requestToPerform.url === "elm-pages-internal://start-spinner") {
       return [requestHash, runStartSpinner(requestToPerform)];
     } else if (requestToPerform.url === "elm-pages-internal://stop-spinner") {
@@ -548,6 +551,15 @@ function runSleep(req) {
   });
 }
 
+async function runWhich(req) {
+  const command = req.body.args[0];
+  try {
+    return jsonResponse(req, await which(command));
+  } catch (error) {
+    return jsonResponse(req, null);
+  }
+}
+
 async function runWriteFileJob(req) {
   const data = req.body.args[0];
   try {

src/Pages/Script.elm

@@ -2,7 +2,7 @@ module Pages.Script exposing
     ( Script
     , withCliOptions, withoutCliOptions
     , writeFile
-    , log, sleep, doThen
+    , log, sleep, doThen, which, expectWhich
     , Error(..)
     )
 
@@ -25,7 +25,7 @@ Read more about using the `elm-pages` CLI to run (or bundle) scripts, plus a bri
 
 ## Utilities
 
-@docs log, sleep, doThen
+@docs log, sleep, doThen, which, expectWhich
 
 
 ## Errors
@@ -189,3 +189,33 @@ doThen : BackendTask error value -> BackendTask error () -> BackendTask error va
 doThen task1 task2 =
     task2
         |> BackendTask.andThen (\() -> task1)
+
+
+{-| -}
+which : String -> BackendTask error (Maybe String)
+which command =
+    BackendTask.Internal.Request.request
+        { body = BackendTask.Http.jsonBody (Encode.string command)
+        , expect = BackendTask.Http.expectJson (Decode.nullable Decode.string)
+        , name = "which"
+        }
+
+
+{-| -}
+expectWhich : String -> BackendTask FatalError String
+expectWhich command =
+    which command
+        |> BackendTask.andThen
+            (\maybePath ->
+                case maybePath of
+                    Just path ->
+                        BackendTask.succeed path
+
+                    Nothing ->
+                        BackendTask.fail
+                            (FatalError.build
+                                { title = "Command not found"
+                                , body = "I expected to find `" ++ command ++ "`, but it was not on your PATH. Make sure it is installed and included in your PATH."
+                                }
+                            )
+            )