Allow to overrride entries of initializationOptions via LS-specific settings

docs/02-usage/050_configuration.md

@@ -250,6 +250,36 @@ Common examples include: `ansible`, `bash`, `bsl`, `clojure`, `cpp`, `cpp_ccls`,
 If `ls_path` is set, Serena's managed download or install is bypassed for that language server.
 In that case, any server-specific version or registry settings do not apply.
 
+(override-init-options)=
+#### Overriding Language Server Initialization Options
+
+When Serena starts a language server, it sends a set of `initializationOptions` as part of the
+Language Server Protocol `initialize` request. These options are constructed internally and are
+tailored to each language server. In some cases, you may want to override or extend these options,
+e.g. to enable a feature or to adjust a behavior that is specific to your setup.
+
+Under the key `initializationOptions` within a language's `ls_specific_settings`, you can provide a
+dictionary of options that is applied on top of the internally constructed `initializationOptions`.
+The values are combined at the top level only: for each top-level key you define, your value
+replaces the original value for that key exactly as given (there is no recursive/deep merge of
+nested dictionaries). Internally constructed keys that you do not define are left unchanged.
+
+* If Serena constructs `initializationOptions` for the language server, each top-level key you
+  provide replaces the internally constructed value for that same key, while all other internally
+  constructed keys are retained.
+* If Serena does not construct any `initializationOptions` for the language server, your custom
+  options are used as-is.
+
+Example:
+
+```yaml
+ls_specific_settings:
+  <language>:
+    initializationOptions:
+      someFeature:
+        enabled: true
+```
+
 #### AL
 
 Serena uses the AL language server bundled in the Microsoft Dynamics 365 Business Central VS Code extension.

src/solidlsp/initialize_params.py

@@ -67,3 +67,16 @@ class DefaultInitializeParamsBuilder(InitializeParamsBuilder):
                 log.info("Additional workspace folders (not indexed by SolidLSP): %s", additional_abs_workspace_paths)
                 workspace_folders.extend([self._create_workspace_folder_entry(abs_path) for abs_path in additional_abs_workspace_paths])
             self._set("workspaceFolders", workspace_folders)
+
+        init_options_key = "initializationOptions"
+        custom_init_options = self._ls.custom_settings.get(init_options_key, None)
+        if custom_init_options:
+            if not isinstance(custom_init_options, dict):
+                log.error("Custom initialization options should be a dictionary, but got %s. Ignoring.", type(custom_init_options).__name__)
+            else:
+                log.info("Applying custom initialization options: %s", custom_init_options)
+                if init_options_key in self._params:
+                    self._params[init_options_key].update(custom_init_options)
+                else:
+                    self._params[init_options_key] = custom_init_options
+                log.info("Final initialization options: %s", self._params[init_options_key])

src/solidlsp/ls.py

@@ -764,6 +764,13 @@ class SolidLanguageServer(ABC):
         """
         self._abs_workspace_folders_all = self._abs_workspace_folders_indexed + self._abs_workspace_folders_additional
 
+    @property
+    def custom_settings(self) -> SolidLSPSettings.CustomLSSettings:
+        """
+        The (user-provided) language server-specific settings.
+        """
+        return self._custom_settings
+
     def _create_dependency_provider(self) -> LanguageServerDependencyProvider:
         """
         Creates the dependency provider for this language server.