feat: add file-based MCP server configuration

com.microsoft.copilot.eclipse.core.test/src/com/microsoft/copilot/eclipse/core/lsp/protocol/CopilotLanguageServerSettingsTests.java

@@ -0,0 +1,195 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT license.
+
+package com.microsoft.copilot.eclipse.core.lsp.protocol;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.Map;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+import com.google.gson.reflect.TypeToken;
+
+/**
+ * Tests for MCP server merge behavior in CopilotLanguageServerSettings.
+ */
+class CopilotLanguageServerSettingsTests {
+
+  private static final String SERVER_A_JSON = "{\"servers\": {\"server-a\": {\"command\": \"echo\"}}}";
+  private static final String KEEP_ME_JSON = "{\"servers\": {\"keep-me\": {\"command\": \"stay\"}}}";
+
+  private CopilotLanguageServerSettings settings;
+  private Gson gson;
+
+  @BeforeEach
+  void setUp() {
+    settings = new CopilotLanguageServerSettings();
+    gson = new GsonBuilder().disableHtmlEscaping().create();
+  }
+
+  // --- setMcpServers ---
+
+  @Test
+  void setMcpServers_withWrappedFormat_extractsServers() {
+    settings.setMcpServers(SERVER_A_JSON);
+
+    String result = getMcpServers();
+    assertNotNull(result);
+    Map<String, Object> servers = parseJsonMap(result);
+    assertEquals(1, servers.size());
+    assertTrue(servers.containsKey("server-a"));
+  }
+
+  @Test
+  void setMcpServers_withBlankInput_doesNotThrow() {
+    settings.setMcpServers("");
+    // blank input is passed through as-is by parseMcpServers
+    String result = getMcpServers();
+    assertEquals("", result);
+  }
+
+  @Test
+  void setMcpServers_withInvalidJson_setsNull() {
+    settings.setMcpServers("not valid json");
+    String result = getMcpServers();
+    assertNull(result);
+  }
+
+  // --- addMcpServers ---
+
+  @Test
+  void addMcpServers_withNoExistingServers_setsServers() {
+    String json = "{\"servers\": {\"new-server\": {\"type\": \"stdio\", \"command\": \"npx\"}}}";
+    settings.addMcpServers(json);
+
+    String result = getMcpServers();
+    assertNotNull(result);
+    Map<String, Object> servers = parseJsonMap(result);
+    assertEquals(1, servers.size());
+    assertTrue(servers.containsKey("new-server"));
+  }
+
+  @Test
+  void addMcpServers_withExistingServers_mergesBothServers() {
+    settings.setMcpServers("{\"servers\": {\"existing-server\": {\"command\": \"a\"}}}");
+
+    settings.addMcpServers("{\"servers\": {\"added-server\": {\"command\": \"b\"}}}");
+
+    String result = getMcpServers();
+    assertNotNull(result);
+    Map<String, Object> servers = parseJsonMap(result);
+    assertEquals(2, servers.size());
+    assertTrue(servers.containsKey("existing-server"));
+    assertTrue(servers.containsKey("added-server"));
+  }
+
+  @Test
+  void addMcpServers_withOverlappingName_laterOverridesEarlier() {
+    settings.setMcpServers("{\"servers\": {\"shared\": {\"command\": \"old-cmd\"}}}");
+    settings.addMcpServers("{\"servers\": {\"shared\": {\"command\": \"new-cmd\"}}}");
+
+    String result = getMcpServers();
+    assertNotNull(result);
+    assertTrue(result.contains("new-cmd"));
+  }
+
+  @Test
+  void addMcpServers_withBlankInput_noChange() {
+    settings.setMcpServers(KEEP_ME_JSON);
+    settings.addMcpServers("");
+
+    String result = getMcpServers();
+    assertNotNull(result);
+    Map<String, Object> servers = parseJsonMap(result);
+    assertEquals(1, servers.size());
+    assertTrue(servers.containsKey("keep-me"));
+  }
+
+  @Test
+  void addMcpServers_withNullInput_noChange() {
+    settings.setMcpServers(KEEP_ME_JSON);
+
+    settings.addMcpServers(null);
+
+    String result = getMcpServers();
+    assertNotNull(result);
+    Map<String, Object> servers = parseJsonMap(result);
+    assertEquals(1, servers.size());
+    assertTrue(servers.containsKey("keep-me"));
+  }
+
+  @Test
+  void addMcpServers_withInvalidJson_noChange() {
+    settings.setMcpServers(KEEP_ME_JSON);
+
+    settings.addMcpServers("not valid json");
+
+    String result = getMcpServers();
+    assertNotNull(result);
+    Map<String, Object> servers = parseJsonMap(result);
+    assertEquals(1, servers.size());
+    assertTrue(servers.containsKey("keep-me"));
+  }
+
+  // --- full merge pipeline: setMcpServers (file-based) + addMcpServers (preferences) + addMcpServers (ext) ---
+
+  @Test
+  void fullMergePipeline_filesThenPrefsThenExtPoints() {
+    // Step 1: file-based servers (lowest priority) via setMcpServers
+    settings.setMcpServers(
+        "{\"servers\": {\"file-only\": {\"command\": \"file-cmd\"}, " + "\"shared\": {\"command\": \"file-shared\"}}}");
+
+    // Step 2: preferences (higher priority) via addMcpServers
+    settings.addMcpServers(
+        "{\"servers\": {\"pref-only\": {\"command\": \"pref-cmd\"}, " + "\"shared\": {\"command\": \"pref-shared\"}}}");
+
+    // Step 3: extension points (highest priority) via addMcpServers
+    settings.addMcpServers(
+        "{\"servers\": {\"ext-only\": {\"command\": \"ext-cmd\"}, " + "\"shared\": {\"command\": \"ext-shared\"}}}");
+
+    String result = getMcpServers();
+    assertNotNull(result);
+    Map<String, Object> servers = parseJsonMap(result);
+
+    // All unique servers present
+    assertEquals(4, servers.size());
+    assertTrue(servers.containsKey("file-only"));
+    assertTrue(servers.containsKey("pref-only"));
+    assertTrue(servers.containsKey("ext-only"));
+
+    // "shared" should have the highest-priority (ext) value
+    assertTrue(servers.containsKey("shared"));
+    assertTrue(result.contains("ext-shared"));
+  }
+
+  @Test
+  void addMcpServers_withMultipleCalls_serversAccumulate() {
+    settings.addMcpServers("{\"servers\": {\"first\": {\"command\": \"1\"}}}");
+    settings.addMcpServers("{\"servers\": {\"second\": {\"command\": \"2\"}}}");
+    settings.addMcpServers("{\"servers\": {\"third\": {\"command\": \"3\"}}}");
+
+    String result = getMcpServers();
+    assertNotNull(result);
+    Map<String, Object> servers = parseJsonMap(result);
+    assertEquals(3, servers.size());
+    assertTrue(servers.containsKey("first"));
+    assertTrue(servers.containsKey("second"));
+    assertTrue(servers.containsKey("third"));
+  }
+
+  private String getMcpServers() {
+    return settings.getGithubSettings().getCopilotSettings().getMcpServers();
+  }
+
+  private Map<String, Object> parseJsonMap(String json) {
+    return gson.fromJson(json, new TypeToken<Map<String, Object>>() {
+    }.getType());
+  }
+}