Avoid using incomplete tmp file for board manager jsons

Fixes arduino#6628

Author: facchinm

arduino-core/src/cc/arduino/contributions/DownloadableContributionsDownloader.java

@@ -52,6 +52,10 @@ public DownloadableContributionsDownloader(File _stagingFolder) {
   }
 
   public File download(DownloadableContribution contribution, Progress progress, final String statusText, ProgressListener progressListener) throws Exception {
+    return download(contribution, progress, statusText, progressListener, false);
+  }
+
+  public File download(DownloadableContribution contribution, Progress progress, final String statusText, ProgressListener progressListener, boolean noResume) throws Exception {
     URL url = new URL(contribution.getUrl());
     Path outputFile = Paths.get(stagingFolder.getAbsolutePath(), contribution.getArchiveFileName());
 
@@ -66,7 +70,7 @@ public File download(DownloadableContribution contribution, Progress progress, f
     while (true) {
       // Need to download or resume downloading?
       if (!Files.isRegularFile(outputFile, LinkOption.NOFOLLOW_LINKS) || (Files.size(outputFile) < contribution.getSize())) {
-        download(url, outputFile.toFile(), progress, statusText, progressListener);
+        download(url, outputFile.toFile(), progress, statusText, progressListener, noResume);
         downloaded = true;
       }
 
@@ -113,6 +117,10 @@ private boolean hasChecksum(DownloadableContribution contribution) {
   }
 
   public void download(URL url, File tmpFile, Progress progress, String statusText, ProgressListener progressListener) throws Exception {
+    download(url, tmpFile, progress, statusText, progressListener, false);
+  }
+
+  public void download(URL url, File tmpFile, Progress progress, String statusText, ProgressListener progressListener, boolean noResume) throws Exception {
     FileDownloader downloader = new FileDownloader(url, tmpFile);
     downloader.addObserver((o, arg) -> {
       FileDownloader me = (FileDownloader) o;
@@ -126,7 +134,7 @@ public void download(URL url, File tmpFile, Progress progress, String statusText
       progress.setProgress(me.getProgress());
       progressListener.onProgress(progress);
     });
-    downloader.download();
+    downloader.download(noResume);
     if (!downloader.isCompleted()) {
       throw new Exception(format(tr("Error downloading {0}"), url), downloader.getError());
     }

arduino-core/src/cc/arduino/contributions/packages/ContributionInstaller.java

@@ -329,7 +329,8 @@ private File download(MultiStepProgress progress, String packageIndexUrl, Progre
     File outputFile = BaseNoGui.indexer.getIndexFile(urlPathParts[urlPathParts.length - 1]);
     File tmpFile = new File(outputFile.getAbsolutePath() + ".tmp");
     DownloadableContributionsDownloader downloader = new DownloadableContributionsDownloader(BaseNoGui.indexer.getStagingFolder());
-    downloader.download(url, tmpFile, progress, statusText, progressListener);
+    boolean noResume = true;
+    downloader.download(url, tmpFile, progress, statusText, progressListener, noResume);
 
     Files.deleteIfExists(outputFile.toPath());
     Files.move(tmpFile.toPath(), outputFile.toPath());

arduino-core/src/cc/arduino/utils/network/FileDownloader.java

@@ -122,10 +122,14 @@ public void setStatus(Status status) {
   }
 
   public void download() throws InterruptedException {
+    download(false);
+  }
+
+  public void download(boolean noResume) throws InterruptedException {
     if ("file".equals(downloadUrl.getProtocol())) {
       saveLocalFile();
     } else {
-      downloadFile();
+      downloadFile(noResume);
     }
   }
 
@@ -140,12 +144,23 @@ private void saveLocalFile() {
   }
 
   private void downloadFile() throws InterruptedException {
+    downloadFile(false);
+  }
+
+  private void downloadFile(boolean noResume) throws InterruptedException {
     RandomAccessFile file = null;
 
     try {
       // Open file and seek to the end of it
       file = new RandomAccessFile(outputFile, "rw");
       initialSize = file.length();
+
+      if (noResume && initialSize > 0) {
+        // delete file and restart downloading
+        Files.delete(outputFile.toPath());
+        initialSize = 0;
+      }
+
       file.seek(initialSize);
 
       setStatus(Status.CONNECTING);