fix: Allow requesting scalar values in workspace/configuration (#649)

fix: Allow requesting scalar values for workspace/configuration

src/main/java/com/redhat/devtools/lsp4ij/client/LanguageClientImpl.java

@@ -10,6 +10,7 @@
  ******************************************************************************/
 package com.redhat.devtools.lsp4ij.client;
 
+import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
 import com.intellij.codeInsight.daemon.DaemonCodeAnalyzer;
 import com.intellij.openapi.Disposable;
@@ -250,15 +251,7 @@ protected Object findSettings(@Nullable String section) {
     }
 
     protected static Object findSettings(String[] sections, JsonObject jsonObject) {
-        JsonObject current = jsonObject;
-        for (String section : sections) {
-            Object result = current.get(section);
-            if (!(result instanceof JsonObject json)) {
-                return null;
-            }
-            current = json;
-        }
-        return current;
+        return SettingsHelper.findSettings(sections, jsonObject);
     }
 
     /**

src/main/java/com/redhat/devtools/lsp4ij/client/SettingsHelper.java

@@ -0,0 +1,47 @@
+/*******************************************************************************
+ * Copyright (c) 2023 Red Hat Inc. and others.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v. 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
+ * which is available at https://www.apache.org/licenses/LICENSE-2.0.
+ *
+ * SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
+ *
+ * Contributors:
+ *     Red Hat Inc. - initial API and implementation
+ *******************************************************************************/
+package com.redhat.devtools.lsp4ij.client;
+
+import com.google.gson.JsonElement;
+import com.google.gson.JsonObject;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+/**
+ * Helpers for extracting nested settings from json
+ */
+public class SettingsHelper {
+
+    private SettingsHelper() {
+    }
+
+    /**
+     * Extract nested settings from json.
+     * @param sections path to the json element to retrieve
+     * @param parent Json to look for settings in
+     * @return the settings retrieved in the specified section and null if the section was not found.
+     */
+    public static @Nullable JsonElement findSettings(@NotNull String[] sections, @Nullable JsonObject parent) {
+        JsonElement current = parent;
+        for (String section : sections) {
+            if (current instanceof JsonObject currentObject) {
+                current = currentObject.get(section);
+                if (current == null) {
+                    return null;
+                }
+            }
+        }
+        return current;
+    }
+}

src/test/java/com/redhat/devtools/lsp4ij/client/SettingsHelperTest.java

@@ -0,0 +1,88 @@
+/*******************************************************************************
+ * Copyright (c) 2023 Red Hat Inc. and others.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v. 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
+ * which is available at https://www.apache.org/licenses/LICENSE-2.0.
+ *
+ * SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
+ *
+ * Contributors:
+ *     Red Hat Inc. - initial API and implementation
+ *******************************************************************************/
+package com.redhat.devtools.lsp4ij.client;
+
+import com.google.gson.JsonElement;
+import com.google.gson.JsonObject;
+import com.google.gson.JsonParser;
+import com.intellij.testFramework.fixtures.BasePlatformTestCase;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.io.StringReader;
+
+/**
+ * Tests for LSP {@link SettingsHelper}.
+ */
+public class SettingsHelperTest extends BasePlatformTestCase {
+    // language=json
+    private final String testJson = """
+            {
+                "mylsp": {
+                    "myscalarsetting": "value",
+                    "myobjectsettings": {
+                        "subsettingA": 1,
+                        "subsettingB": 2
+                    }
+                }
+            }
+            """;
+
+    private static void assertFindSettings(@NotNull String json, @NotNull String[] sections, @Nullable String expectedJsonText) {
+        JsonObject jsonObject = JsonParser.parseReader(new StringReader(json)).getAsJsonObject();
+        JsonElement expectedJson = expectedJsonText == null ? null : JsonParser.parseReader(new StringReader(expectedJsonText));
+
+        JsonElement result = SettingsHelper.findSettings(sections, jsonObject);
+
+        assertEquals(result, expectedJson);
+    }
+
+    public void testGetSettingsIdentityOnEmptySections() {
+        String[] requestedPath = new String[0];
+        assertFindSettings(testJson, requestedPath, testJson);
+    }
+
+    public void testGetSettingsObjectValue() {
+        String[] requestedPath = new String[]{"mylsp"};
+        assertFindSettings(testJson, requestedPath, """
+                {
+                    "myscalarsetting": "value",
+                    "myobjectsettings": {
+                        "subsettingA": 1,
+                        "subsettingB": 2
+                    }
+                }
+                """);
+    }
+
+    public void testGetSettingsPrimitiveValue() {
+        String[] requestedPath = new String[]{"mylsp", "myscalarsetting"};
+        assertFindSettings(testJson, requestedPath, "\"value\"");
+    }
+
+    public void testGetSettingsDeepPrimitiveValue() {
+        String[] requestedPath = new String[]{"mylsp", "myobjectsettings", "subsettingA"};
+        assertFindSettings(testJson, requestedPath, "1");
+    }
+
+    public void testGetSettingsNonExistingValue() {
+        String[] requestedPath = new String[]{"mylsp", "nonexistant"};
+        assertFindSettings(testJson, requestedPath, null);
+    }
+
+    public void testGetSettingsEmptyJson() {
+        String[] requestedPath = new String[]{"mylsp", "myobjectsettings", "subsettingA"};
+        assertFindSettings("{}", requestedPath, null);
+    }
+}