Fix regression in the URL launcher config

Due to the merging of configuration files on all platforms, it has been
made impossible to completely disable URL launching without still
executing some kind of program like `true`.

Setting the launcher to `None` in the config, will now disable it
completely.

This fixes #2058.

CHANGELOG.md

@@ -8,7 +8,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ### Changed
 
-- Smoother scrolling for touchpads (also affects scrolling with some mice that send fractional scrolling values)
+- Improve scrolling accuracy with devices sending fractional updates (like touchpads)
 - `scrolling.multiplier` now affects normal scrolling with touchpads
 
 ### Fixed
@@ -17,6 +17,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Excessive polling every 100ms with `live_config_reload` enabled
 - Unicode characters at the beginning of URLs are now properly ignored
 - Remove error message when reloading an empty config
+- Allow disabling URL launching by setting the value of `mouse.url.launcher` to `None`
 
 ## Version 0.2.7
 

alacritty.yml

@@ -291,6 +291,8 @@ mouse:
     # This program is executed when clicking on a text which is recognized as a URL.
     # The URL is always added to the command as the last parameter.
     #
+    # When set to `None`, URL launching will be disabled completely.
+    #
     # Default:
     #   - (macOS) open
     #   - (Linux) xdg-open

src/config/mod.rs

@@ -116,7 +116,7 @@ pub struct Mouse {
 #[derive(Clone, Debug, Deserialize, PartialEq, Eq)]
 pub struct Url {
     // Program for opening links
-    #[serde(deserialize_with = "failure_default")]
+    #[serde(deserialize_with = "deserialize_launcher")]
     pub launcher: Option<CommandWrapper>,
 
     // Modifier used to open links
@@ -124,6 +124,34 @@ pub struct Url {
     pub modifiers: ModifiersState,
 }
 
+fn deserialize_launcher<'a, D>(deserializer: D) -> ::std::result::Result<Option<CommandWrapper>, D::Error>
+    where D: de::Deserializer<'a>
+{
+    let default = Url::default().launcher;
+
+    // Deserialize to generic value
+    let val = match serde_yaml::Value::deserialize(deserializer) {
+        Ok(val) => val,
+        Err(err) => {
+            error!("Problem with config: {}; using {}", err, default.clone().unwrap().program());
+            return Ok(default);
+        },
+    };
+
+    // Accept `None` to disable the launcher
+    if val.as_str().filter(|v| v.to_lowercase() == "none").is_some() {
+        return Ok(None);
+    }
+
+    match <Option<CommandWrapper>>::deserialize(val) {
+        Ok(launcher) => Ok(launcher),
+        Err(err) => {
+            error!("Problem with config: {}; using {}", err, default.clone().unwrap().program());
+            Ok(default)
+        },
+    }
+}
+
 impl Default for Url {
     fn default() -> Url {
         Url {