make loading of workspace languages.toml files optional and disable it by default

book/src/languages.md

@@ -28,8 +28,13 @@ There are three possible locations for a `languages.toml` file:
 
 3. In a `.helix` folder in your project. Language configuration may also be
    overridden local to a project by creating a `languages.toml` file in a
-   `.helix` folder. Its settings will be merged with the language configuration
-   in the configuration directory and the built-in configuration.
+   `.helix` folder and adding `workspace-config = true` to the top of your
+   configuration directory `languages.toml`. Its settings will be merged with
+   the language configuration in the configuration directory and the built-in
+   configuration. Enabling workspace configs is a potential security risk.
+   A project from an untrusted sources may e.g. contain a
+   `.helix/languages.toml` that modifies a language server command to execute
+   malicious code on your machine.
 
 ## Language configuration
 

helix-loader/src/config.rs

@@ -1,4 +1,5 @@
 use std::str::from_utf8;
+use std::path::PathBuf;
 
 /// Default built-in languages.toml.
 pub fn default_lang_config() -> toml::Value {
@@ -7,40 +8,28 @@ pub fn default_lang_config() -> toml::Value {
         .expect("Could not parse built-in languages.toml to valid toml")
 }
 
+fn merge_language_config(
+    left: toml::Value, file: PathBuf,
+) -> Result<toml::Value, toml::de::Error> {
+    let right = std::fs::read_to_string(file).ok()
+        .map(|c| toml::from_str(&c)).transpose()?;
+
+    let config = match right {
+        Some(right) => crate::merge_toml_values(left, right, 3),
+        None => left,
+    };
+
+    Ok(config)
+}
+
 /// User configured languages.toml file, merged with the default config.
 pub fn user_lang_config() -> Result<toml::Value, toml::de::Error> {
-    let config = [
-        crate::config_dir(),
-        crate::find_workspace().0.join(".helix"),
-    ]
-    .into_iter()
-    .map(|path| path.join("languages.toml"))
-    .filter_map(|file| {
-        std::fs::read_to_string(file)
-            .map(|config| toml::from_str(&config))
-            .ok()
-    })
-    .collect::<Result<Vec<_>, _>>()?
-    .into_iter()
-    .fold(default_lang_config(), |a, b| {
-        // combines for example
-        // b:
-        //   [[language]]
-        //   name = "toml"
-        //   language-server = { command = "taplo", args = ["lsp", "stdio"] }
-        //
-        // a:
-        //   [[language]]
-        //   language-server = { command = "/usr/bin/taplo" }
-        //
-        // into:
-        //   [[language]]
-        //   name = "toml"
-        //   language-server = { command = "/usr/bin/taplo" }
-        //
-        // thus it overrides the third depth-level of b with values of a if they exist, but otherwise merges their values
-        crate::merge_toml_values(a, b, 3)
-    });
+    let global = merge_language_config(default_lang_config(), crate::lang_config_file())?;
+
+    let config = match global.get("workspace-config").and_then(|v| v.as_bool()) {
+        Some(true) => merge_language_config(global, crate::workspace_lang_config_file())?,
+        _ => global,
+    };
 
     Ok(config)
 }

languages.toml

@@ -1,6 +1,8 @@
 # Language support configuration.
 # See the languages documentation: https://docs.helix-editor.com/master/languages.html
 
+workspace-config = false
+
 use-grammars = { except = [ "hare", "wren", "gemini" ] }
 
 [language-server]