Fallback to stock library_index.json file if the copy in .arduino15 is missing/corrupted or if it the downloaded one if corrupted. Fixes arduino#3778

Author: Federico Fissore

arduino-core/src/cc/arduino/contributions/libraries/LibrariesIndexer.java

@@ -109,6 +109,11 @@ public void rescanLibraries() {
     // Clear all installed flags
     installedLibraries.clear();
     installedLibrariesWithDuplicates.clear();
+
+    if (index.getLibraries() == null) {
+      return;
+    }
+
     for (ContributedLibrary lib : index.getLibraries()) {
       lib.setInstalled(false);
     }

arduino-core/src/processing/app/BaseNoGui.java

@@ -592,11 +592,7 @@ static public void initPackages() throws Exception {
 
     try {
       indexer.parseIndex();
-    } catch (JsonProcessingException e) {
-      FileUtils.deleteIfExists(indexFile);
-      FileUtils.deleteIfExists(indexSignatureFile);
-      throw e;
-    } catch (SignatureVerificationFailedException e) {
+    } catch (JsonProcessingException | SignatureVerificationFailedException e) {
       FileUtils.deleteIfExists(indexFile);
       FileUtils.deleteIfExists(indexSignatureFile);
       throw e;
@@ -611,6 +607,17 @@ static public void initPackages() throws Exception {
 
     librariesIndexer = new LibrariesIndexer(BaseNoGui.getSettingsFolder(), indexer);
     File librariesIndexFile = librariesIndexer.getIndexFile();
+    copyStockLibraryIndexIfUpstreamIsMissing(librariesIndexFile);
+    try {
+      librariesIndexer.parseIndex();
+    } catch (JsonProcessingException e) {
+      FileUtils.deleteIfExists(librariesIndexFile);
+      copyStockLibraryIndexIfUpstreamIsMissing(librariesIndexFile);
+      librariesIndexer.parseIndex();
+    }
+  }
+
+  private static void copyStockLibraryIndexIfUpstreamIsMissing(File librariesIndexFile) throws IOException {
     if (!librariesIndexFile.isFile()) {
       File defaultLibraryJsonFile = new File(getContentFile("dist"), "library_index.json");
       if (defaultLibraryJsonFile.isFile()) {
@@ -628,12 +635,6 @@ static public void initPackages() throws Exception {
         }
       }
     }
-    try {
-      librariesIndexer.parseIndex();
-    } catch (JsonProcessingException e) {
-      FileUtils.deleteIfExists(librariesIndexFile);
-      throw e;
-    }
   }
 
   static protected void initPlatform() {