From 29fdd5dc4ba929b82edefa383aa918692b73a222 Mon Sep 17 00:00:00 2001
From: Julius Krumbiegel <julius.krumbiegel@gmail.com>
Date: Thu, 19 Sep 2024 13:34:35 +0200
Subject: [PATCH 1/2] Catch failure to open Worker and write out port

---
 src/Malt.jl        | 26 ++++++++++++++++++++------
 test/exceptions.jl |  5 +++++
 2 files changed, 25 insertions(+), 6 deletions(-)

diff --git a/src/Malt.jl b/src/Malt.jl
index 043392e..8e91d61 100644
--- a/src/Malt.jl
+++ b/src/Malt.jl
@@ -103,11 +103,18 @@ mutable struct Worker <: AbstractWorker
     function Worker(; env=String[], exeflags=[])
         # Spawn process
         cmd = _get_worker_cmd(; env, exeflags)
-        proc = open(Cmd(
-            cmd; 
-            detach=true,
-            windows_hide=true,
-        ), "w+")
+        err = Pipe()
+        proc = open(
+            pipeline(
+                Cmd(
+                    cmd; 
+                    detach=true,
+                    windows_hide=true,
+                ),
+                stderr = err
+            ),
+            "w+"
+        )
         
         # Keep internal list
         __iNtErNaL_get_running_procs()
@@ -115,7 +122,14 @@ mutable struct Worker <: AbstractWorker
 
         # Block until reading the port number of the process (from its stdout)
         port_str = readline(proc)
-        port = parse(UInt16, port_str)
+        port = tryparse(UInt16, port_str)
+        if port === nothing
+            Base.kill(proc, Base.SIGTERM)
+            close(err.in)
+            err_t = Threads.@spawn read(err, String)
+            err_output = fetch(err_t)
+            error("""Failed to start worker process correctly. Expected to read port from stdout, got "$port_str" instead. Stderr output was:\n$err_output""")
+        end
 
         # Connect
         socket = Sockets.connect(port)
diff --git a/test/exceptions.jl b/test/exceptions.jl
index 98c4dc8..ea29828 100644
--- a/test/exceptions.jl
+++ b/test/exceptions.jl
@@ -147,3 +147,8 @@ struct LocalStruct end
     m.stop(w)
     @test !m.isrunning(w)
 end
+
+@testset "Failure to spin up Worker" begin
+    e = @catcherror Malt.Worker(; exeflags = ["-t invalid"])
+    @test occursin("ERROR: julia: -t", e.msg)
+end

From 7329df546b866200b2ab0e83e88a08c1bc898fb5 Mon Sep 17 00:00:00 2001
From: Fons van der Plas <fonsvdplas@gmail.com>
Date: Thu, 3 Oct 2024 21:48:19 +0200
Subject: [PATCH 2/2] Update test/exceptions.jl

---
 test/exceptions.jl | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/test/exceptions.jl b/test/exceptions.jl
index ea29828..5325ca9 100644
--- a/test/exceptions.jl
+++ b/test/exceptions.jl
@@ -149,6 +149,6 @@ struct LocalStruct end
 end
 
 @testset "Failure to spin up Worker" begin
-    e = @catcherror Malt.Worker(; exeflags = ["-t invalid"])
+    e = @catcherror m.Worker(; exeflags = ["-t invalid"])
     @test occursin("ERROR: julia: -t", e.msg)
 end