feat(config): add undo_backspace option

espanso-config/src/config/mod.rs

@@ -117,6 +117,10 @@ pub trait Config: Send + Sync {
   // Hotkey used to trigger the Search UI
   fn search_shortcut(&self) -> Option<String>;
 
+  // When enabled, espanso automatically "reverts" an expansion if the user
+  // presses the Backspace key afterwards.
+  fn undo_backspace(&self) -> bool;
+
   fn is_match<'a>(&self, app: &AppProperties<'a>) -> bool;
 
   fn pretty_dump(&self) -> String {

espanso-config/src/config/parse/mod.rs

@@ -39,6 +39,7 @@ pub(crate) struct ParsedConfig {
   pub apply_patch: Option<bool>,
   pub search_trigger: Option<String>,
   pub search_shortcut: Option<String>,
+  pub undo_backspace: Option<bool>,
 
   pub pre_paste_delay: Option<usize>,
   pub restore_clipboard_delay: Option<usize>,

espanso-config/src/config/parse/yaml.rs

@@ -88,6 +88,9 @@ pub(crate) struct YAMLConfig {
   #[serde(default)]
   pub search_shortcut: Option<String>,
 
+  #[serde(default)]
+  pub undo_backspace: Option<bool>,
+
   // Include/Exclude
   #[serde(default)]
   pub includes: Option<Vec<String>>,
@@ -163,6 +166,7 @@ impl TryFrom<YAMLConfig> for ParsedConfig {
       }),
       search_trigger: yaml_config.search_trigger,
       search_shortcut: yaml_config.search_shortcut,
+      undo_backspace: yaml_config.undo_backspace,
 
       pre_paste_delay: yaml_config.pre_paste_delay,
       restore_clipboard_delay: yaml_config.restore_clipboard_delay,
@@ -216,6 +220,7 @@ mod tests {
       options: test_options
     search_trigger: "search"
     search_shortcut: "CTRL+SPACE"
+    undo_backspace: false
       
     use_standard_includes: true
     includes: ["test1"]
@@ -261,6 +266,7 @@ mod tests {
         keyboard_layout: Some(keyboard_layout),
         search_trigger: Some("search".to_owned()),
         search_shortcut: Some("CTRL+SPACE".to_owned()),
+        undo_backspace: Some(false),
 
         pre_paste_delay: Some(300),
 

espanso-config/src/config/resolve.rs

@@ -290,6 +290,10 @@ impl Config for ResolvedConfig {
       None => Some("ALT+SPACE".to_string()),
     }
   }
+
+  fn undo_backspace(&self) -> bool {
+    self.parsed.undo_backspace.unwrap_or(true)
+  }
 }
 
 impl ResolvedConfig {
@@ -365,6 +369,7 @@ impl ResolvedConfig {
       keyboard_layout,
       search_trigger,
       search_shortcut,
+      undo_backspace,
       includes,
       excludes,
       extra_includes,

espanso-config/src/legacy/mod.rs

@@ -366,6 +366,10 @@ impl Config for LegacyInteropConfig {
   fn search_shortcut(&self) -> Option<String> {
     None
   }
+
+  fn undo_backspace(&self) -> bool {
+    self.config.undo_backspace
+  }
 }
 
 struct LegacyMatchGroup {