Fix regression: do not crash on board list if a discovery is not properly installed (#1814)

* Added tests for #1669

* Fixed regession in discoveries startup

Fix #1669

Author: cmaglie

Diff for: arduino/discovery/discovery.go

@@ -247,29 +247,32 @@ func (disc *PluggableDiscovery) runProcess() error {
 		return err
 	}
 	disc.outgoingCommandsPipe = stdin
-	disc.process = proc
 
 	messageChan := make(chan *discoveryMessage)
 	disc.incomingMessagesChan = messageChan
 	go disc.jsonDecodeLoop(stdout, messageChan)
 
-	if err := disc.process.Start(); err != nil {
+	if err := proc.Start(); err != nil {
 		return err
 	}
+
 	disc.statusMutex.Lock()
 	defer disc.statusMutex.Unlock()
+	disc.process = proc
 	disc.state = Alive
 	logrus.Infof("started discovery %s process", disc.id)
 	return nil
 }
 
 func (disc *PluggableDiscovery) killProcess() error {
 	logrus.Infof("killing discovery %s process", disc.id)
-	if err := disc.process.Kill(); err != nil {
-		return err
-	}
-	if err := disc.process.Wait(); err != nil {
-		return err
+	if disc.process != nil {
+		if err := disc.process.Kill(); err != nil {
+			return err
+		}
+		if err := disc.process.Wait(); err != nil {
+			return err
+		}
 	}
 	disc.statusMutex.Lock()
 	defer disc.statusMutex.Unlock()

Diff for: test/test_board.py

@@ -14,6 +14,8 @@
 # a commercial license, send an email to [email protected].
 from pathlib import Path
 from git import Repo
+import os
+import glob
 import simplejson as json
 import semver
 import pytest
@@ -405,6 +407,23 @@ def test_board_list(run_command):
         assert "protocol_label" in port["port"]
 
 
+def test_board_list_with_invalid_discovery(run_command, data_dir):
+    run_command(["core", "update-index"])
+    result = run_command(["board", "list"])
+    assert result.ok
+
+    # check that the CLI do no crash if an invalid discovery is installed
+    # (for example if the installation fails midway).
+    # https://github.com/arduino/arduino-cli/issues/1669
+    tool_dir = os.path.join(data_dir, "packages", "builtin", "tools", "serial-discovery")
+    for file_to_delete in glob.glob(tool_dir + "/*/*"):
+        os.remove(file_to_delete)
+
+    result = run_command(["board", "list"])
+    assert result.ok
+    assert "builtin:serial-discovery" in result.stderr
+
+
 def test_board_listall(run_command):
     assert run_command(["update"])
     assert run_command(["core", "install", "arduino:[email protected]"])