ServerAPI fallback logic when FileAPI not supported (#1051)

* ServerAPI fallback logic when FileAPI not supported.

* Update CHANGELOG.md

* Remove fileapi fix entry because the main feature ships with this same release

Author: andreeis

src/cmake-tools.ts

@@ -281,15 +281,27 @@ export class CMakeTools implements vscode.Disposable, api.CMakeToolsAPI {
       } else {
         communicationMode = 'legacy';
       }
-
-      if (communicationMode != 'fileapi' && communicationMode != 'serverapi') {
-        log.warning(
-          localize('please.upgrade.cmake',
-            'For the best experience, CMake server or file-api support is required. Please upgrade CMake to {0} or newer.',
-            versionToString(cmake.minimalServerModeVersion)));
+    } else if (communicationMode == 'fileapi') {
+      if (!cmake.isFileApiModeSupported) {
+        if (cmake.isServerModeSupported) {
+          communicationMode = 'serverapi';
+          log.warning(
+            localize('switch.to.serverapi',
+              'CMake file-api communication mode is not supported in versions earlier than {0}. Switching to CMake server communication mode.',
+              versionToString(cmake.minimalFileApiModeVersion)));
+        } else {
+          communicationMode = 'legacy';
+        }
       }
     }
 
+    if (communicationMode != 'fileapi' && communicationMode != 'serverapi') {
+      log.warning(
+        localize('please.upgrade.cmake',
+          'For the best experience, CMake server or file-api support is required. Please upgrade CMake to {0} or newer.',
+          versionToString(cmake.minimalServerModeVersion)));
+    }
+
     try {
       this._statusMessage.set(localize('starting.cmake.driver.status', 'Starting CMake Server...'));
       switch (communicationMode) {

src/cmake/cmake-executable.ts

@@ -16,7 +16,7 @@ export async function getCMakeExecutableInformation(path: string): Promise<CMake
     path,
     isPresent: false,
     minimalServerModeVersion: util.parseVersion('3.7.1'),
-    minimalFileApiModeVersion: util.parseVersion('3.15.0'),
+    minimalFileApiModeVersion: util.parseVersion('3.14.0'),
   };
 
   if (path.length != 0) {