editor: Fix function completion expansion in string contexts and call expressions (#30351)

Closes #27582

Now, when accepting function completion, it doesn't expand with
parentheses and arguments in the following cases:
1. If it's in a string (like `type Foo = MyClass["sayHello"]` instead of
`type Foo = MyClass["sayHello(name)"]`)
2. If it's in a call expression (like `useRef<HTMLDivElement>(null)`
over `useRef(initialValue)<HTMLDivElement>(null)`)

This is a follow-up to https://github.com/zed-industries/zed/pull/30312,
more like cleaner version of it.

Release Notes:

- Fixed an issue where accepting a method as an object string in
JavaScript would incorrectly expand. E.g. `MyClass["sayHello(name)"]`
instead of `MyClass["sayHello"]`.

crates/language/src/language.rs

@@ -828,6 +828,8 @@ pub struct LanguageConfigOverride {
     pub completion_query_characters: Override<HashSet<char>>,
     #[serde(default)]
     pub opt_into_language_servers: Vec<LanguageServerName>,
+    #[serde(default)]
+    pub prefer_label_for_snippet: Option<bool>,
 }
 
 #[derive(Clone, Deserialize, Debug, Serialize, JsonSchema)]
@@ -1788,6 +1790,18 @@ impl LanguageScope {
         )
     }
 
+    /// Returns whether to prefer snippet `label` over `new_text` to replace text when
+    /// completion is accepted.
+    ///
+    /// In cases like when cursor is in string or renaming existing function,
+    /// you don't want to expand function signature instead just want function name
+    /// to replace existing one.
+    pub fn prefers_label_for_snippet_in_completion(&self) -> bool {
+        self.config_override()
+            .and_then(|o| o.prefer_label_for_snippet)
+            .unwrap_or(false)
+    }
+
     /// Returns a list of bracket pairs for a given language with an additional
     /// piece of information about whether the particular bracket pair is currently active for a given language.
     pub fn brackets(&self) -> impl Iterator<Item = (&BracketPair, bool)> {