From 3dcfb5c0fc5fda1c72ab120def9d79417afb739b Mon Sep 17 00:00:00 2001
From: Marco Roth <marco.roth@intergga.ch>
Date: Wed, 14 Oct 2026 17:09:24 +0900
Subject: [PATCH] Raise on unknown browsers in `targets`

---
 README.md                         |  2 ++
 rust/src/options.rs               | 22 +++++++++++++++++++++-
 test/lightningcss/targets_test.rb | 24 ++++++++++++++++++++++++
 3 files changed, 47 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index ad12170..852f1ef 100644
--- a/README.md
+++ b/README.md
@@ -76,6 +76,8 @@ LightningCSS.transform(".a { color: oklch(60% .2 30) }", targets: { safari: "15.
 
 Prefer a `String` for a minor version above 9, since `16.10` as a `Float` is `16.1`.
 
+The browsers it reads are `android`, `chrome`, `edge`, `firefox`, `ie`, `ios_saf` (or `ios`), `opera`, `safari`, and `samsung`. Any other name raises a `LightningCSS::OptionError`.
+
 #### Bundling
 
 `bundle` resolves the `@import` statements a stylesheet was written with by reading the files they name, so it takes a path on disk to the entry stylesheet.
diff --git a/rust/src/options.rs b/rust/src/options.rs
index 42f7c20..732bc92 100644
--- a/rust/src/options.rs
+++ b/rust/src/options.rs
@@ -102,12 +102,32 @@ impl Version {
   }
 }
 
+const BROWSERS: [&str; 10] = [
+  "android", "chrome", "edge", "firefox", "ie", "ios", "ios_saf", "opera", "safari", "samsung",
+];
+
 impl TransformOptions {
   pub fn to_targets(&self) -> Result<Targets, String> {
     let Some(versions) = &self.targets else {
       return Ok(Targets::default());
     };
 
+    let mut unknown: Vec<&str> = versions
+      .keys()
+      .map(String::as_str)
+      .filter(|name| !BROWSERS.contains(name))
+      .collect();
+
+    if !unknown.is_empty() {
+      unknown.sort_unstable();
+
+      return Err(format!(
+        "Unknown browser{} in targets: {}",
+        if unknown.len() > 1 { "s" } else { "" },
+        unknown.join(", ")
+      ));
+    }
+
     let mut browsers = Browsers::default();
 
     for (name, version) in versions {
@@ -127,7 +147,7 @@ impl TransformOptions {
         "opera" => browsers.opera = encoded,
         "safari" => browsers.safari = encoded,
         "samsung" => browsers.samsung = encoded,
-        _ => {}
+        _ => unreachable!(),
       }
     }
 
diff --git a/test/lightningcss/targets_test.rb b/test/lightningcss/targets_test.rb
index f484832..636dd0b 100644
--- a/test/lightningcss/targets_test.rb
+++ b/test/lightningcss/targets_test.rb
@@ -85,6 +85,30 @@ class TargetsTest < Minitest::Spec
       end
     end
 
+    test "raises an option error for a browser it does not know" do
+      error = assert_raises(OptionError) { LightningCSS.transform(".a{}", targets: { safar: 15 }) }
+
+      assert_equal "Unknown browser in targets: safar", error.message
+    end
+
+    test "names every browser it does not know, in order" do
+      error = assert_raises(OptionError) { LightningCSS.transform(".a{}", targets: { netscape: 4, chrome: 100, mosaic: 1 }) }
+
+      assert_equal "Unknown browsers in targets: mosaic, netscape", error.message
+    end
+
+    test "raises for a browser it does not know before reading any version" do
+      error = assert_raises(OptionError) { LightningCSS.transform(".a{}", targets: { safari: "x", safar: 15 }) }
+
+      assert_equal "Unknown browser in targets: safar", error.message
+    end
+
+    test "reads ios as ios_saf" do
+      code = LightningCSS.transform(".a { color: oklch(60% .2 30) }", targets: { ios: "15.4" }, minify: true).code
+
+      assert_equal ".a{color:oklch(60% .2 30)}", code
+    end
+
     test "raises an option error for a negative version" do
       error = assert_raises(OptionError) { LightningCSS.transform(".a{}", targets: { safari: -1 }) }