From 2268d505970604f38738bda758ffac44a2a77e54 Mon Sep 17 00:00:00 2001
From: "Andres G. Aragoneses" <knocte@gmail.com>
Date: Sat, 12 Aug 2023 14:00:18 +0800
Subject: [PATCH] Fsdk: fix VsWhere when no entries are returned

Otherwise First() would fail with IOE: Sequence contains no
elements.
---
 Fsdk/Process.fs      | 11 ++++++-----
 fsxc/Fsxc.fs         |  5 ++++-
 scripts/make.fsx     |  4 +++-
 scripts/runTests.fsx |  5 ++++-
 test/testProcess.fsx |  4 +++-
 5 files changed, 20 insertions(+), 9 deletions(-)

diff --git a/Fsdk/Process.fs b/Fsdk/Process.fs
index 9b88ba59..7da5298b 100644
--- a/Fsdk/Process.fs
+++ b/Fsdk/Process.fs
@@ -496,7 +496,7 @@ module Process =
             commandNamesByOrderOfPreference
 
     // FIXME: it returns the first result, but we should return all (array<string>)
-    let VsWhere(searchPattern: string) : string =
+    let VsWhere(searchPattern: string) : Option<string> =
         if Misc.GuessPlatform() <> Misc.Platform.Windows then
             failwith "vswhere.exe doesn't exist in other platforms than Windows"
 
@@ -523,14 +523,15 @@ module Process =
 
         let procResult = Execute(vswhereCmd, Echo.Off)
 
-        let firstResult =
+        let entries =
             procResult
                 .UnwrapDefault()
                 .Split(
                     Array.singleton Environment.NewLine,
                     StringSplitOptions.RemoveEmptyEntries
                 )
-                .First()
-                .Trim()
 
-        firstResult
+        if entries.Any() then
+            entries.First().Trim() |> Some
+        else
+            None
diff --git a/fsxc/Fsxc.fs b/fsxc/Fsxc.fs
index 8f92ea8d..77cb91e8 100644
--- a/fsxc/Fsxc.fs
+++ b/fsxc/Fsxc.fs
@@ -788,7 +788,10 @@ let fsi = { CommandLineArgs = System.Environment.GetCommandLineArgs() }
                 "dotnet"
 #else
                 match Misc.GuessPlatform() with
-                | Misc.Platform.Windows -> Process.VsWhere "**\\fsc.exe"
+                | Misc.Platform.Windows ->
+                    match Process.VsWhere "**\\fsc.exe" with
+                    | None -> failwith "fsc.exe not found"
+                    | Some fscExe -> fscExe
                 | _ -> "fsharpc"
 #endif
 
diff --git a/scripts/make.fsx b/scripts/make.fsx
index 99cab4d4..42fc565e 100644
--- a/scripts/make.fsx
+++ b/scripts/make.fsx
@@ -91,7 +91,9 @@ let FindBuildTool() : string * string =
 #if !LEGACY_FRAMEWORK
         "dotnet", "build"
 #else
-        (Process.VsWhere "MSBuild\\**\\Bin\\MSBuild.exe"), String.Empty
+        match Process.VsWhere "MSBuild\\**\\Bin\\MSBuild.exe" with
+        | None -> failwith "msbuild not found?"
+        | Some msbuildExe -> msbuildExe, String.Empty
 #endif
 
 let BuildSolution
diff --git a/scripts/runTests.fsx b/scripts/runTests.fsx
index dc1a6da8..102ccd4a 100755
--- a/scripts/runTests.fsx
+++ b/scripts/runTests.fsx
@@ -72,7 +72,10 @@ let fsharpCompilerCommand =
     "dotnet"
 #else
     match Misc.GuessPlatform() with
-    | Misc.Platform.Windows -> Process.VsWhere "**\\fsc.exe"
+    | Misc.Platform.Windows ->
+        match Process.VsWhere "**\\fsc.exe" with
+        | None -> failwith "fsc.exe not found"
+        | Some fscExe -> fscExe
     | _ -> "fsharpc"
 #endif
 
diff --git a/test/testProcess.fsx b/test/testProcess.fsx
index a6e28a52..3dc35aab 100755
--- a/test/testProcess.fsx
+++ b/test/testProcess.fsx
@@ -26,7 +26,9 @@ let command =
     if Misc.GuessPlatform() = Misc.Platform.Windows then
         // HACK: we should call fsx here but then we would get this problem in
         // the tests: error FS0193: The process cannot access the file 'D:\a\fsx\fsx\test\bin\FSharp.Core.dll' because it is being used by another process.
-        Process.VsWhere "**\\fsi.exe"
+        match Process.VsWhere "**\\fsi.exe" with
+        | None -> failwith "fsi.exe not found"
+        | Some fsiExe -> fsiExe
     else
         // FIXME: extract PREFIX from build.config instead of assuming default
         "/usr/local/bin/fsx"