From 37a9c1b7b8072afd2de4871ab9835548d785e3cd Mon Sep 17 00:00:00 2001
From: egasato <github@egasato.me>
Date: Wed, 11 Feb 2026 21:58:21 +0100
Subject: [PATCH] Force UTF-8 with BOM for Windows PowerShell shebang recipes

Windows PowerShell (`powershell.exe`) is included in all modern Windows
installs, and it's usual to leverage it when a recipe is complex enough
to require basic control flow constructs (which `cmd.exe` usually lacks
or it's unreadable).

The default encoding (codepage) used by `conhost.exe` (Console Window
Host) may vary depending on the display language and region of the
system (e.g. 437 for US English, 850 for Western European languages),
but it's certainly never UTF-8 (codepage 65001; still an experimental
feature that has to be enabled system-wide).

Forcing the UTF-8 Byte Order Mark to be present when the shebang recipe
is for Windows PowerShell fixes many output encoding issues.
---
 src/lib.rs    |  1 +
 src/recipe.rs | 22 ++++++++++++++++++----
 2 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/src/lib.rs b/src/lib.rs
index b633a1d65d..453cb511a5 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -42,6 +42,7 @@ pub(crate) use {
     expression::Expression,
     format_string_part::FormatStringPart,
     fragment::Fragment,
+    fs::File,
     function::Function,
     interpreter::Interpreter,
     invocation::Invocation,
diff --git a/src/recipe.rs b/src/recipe.rs
index daa63c910c..751ead13bd 100644
--- a/src/recipe.rs
+++ b/src/recipe.rs
@@ -467,10 +467,24 @@ impl<'src, D> Recipe<'src, D> {
       eprintln!("{}", config.color.doc().stderr().paint(&script));
     }
 
-    fs::write(&path, script).map_err(|error| Error::TempdirIo {
-      recipe: self.name(),
-      io_error: error,
-    })?;
+    let interpreter = match &executor {
+      Executor::Shebang(shebang) => shebang.interpreter,
+      Executor::Command(command) => command.command.as_str(),
+    };
+    let preamble = match interpreter.to_lowercase().as_str() {
+      "powershell" | "powershell.exe" => "\u{FEFF}",
+      _ => "",
+    };
+
+    File::create(&path)
+      .and_then(|mut f| {
+        f.write_all(preamble.as_ref())?;
+        f.write_all(script.as_ref())
+      })
+      .map_err(|error| Error::TempdirIo {
+        recipe: self.name(),
+        io_error: error,
+      })?;
 
     let mut command = executor.command(
       config,