Fixes #3842

src/Fable.Cli/CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Fixed
 
+* [All] Fixed Fable compiler hanging on some errors (#3842) (by @ncave)
 * [JS/TS] Fixed DateTime.MinValue, DateTime.MaxValue (#3836) (by @ncave)
 
 ## 4.19.0 - 2024-06-10

src/Fable.Cli/Entry.fs

@@ -385,7 +385,7 @@ type Runner =
 
             let startCompilation () =
                 State.Create(cliArgs, ?watchDelay = watchDelay, useMSBuildForCracking = useMSBuildForCracking)
-                |> startCompilation
+                |> startCompilationAsync
                 |> Async.RunSynchronously
 
             return!

src/Fable.Cli/Main.fs

@@ -1250,7 +1250,7 @@ let private compilationCycle (state: State) (changes: ISet<string>) =
 
 type FileWatcherMsg = | Changes of timeStamp: DateTime * changes: ISet<string>
 
-let startCompilation state =
+let startCompilationAsync state =
     async {
         try
             let state =

src/Fable.Transforms/State.fs

@@ -139,7 +139,12 @@ type ImplFile =
 
         // add all entities to the entity cache
         let entities = Dictionary()
-        let declarations = file.Declarations
+
+        let declarations =
+            try
+                file.Declarations // this may throw
+            with _ex ->
+                []
 
         FSharp2Fable.Compiler.getRootFSharpEntities declarations |> loop entities
 

tests/Integration/Compiler/Util/Compiler.fs

@@ -69,7 +69,7 @@ module Compiler =
 
         let result =
             state
-            |> startCompilation
+            |> startCompilationAsync
             |> Async.RunSynchronously
 
         match result with