fix: Provide info on file name when Json parsing fails (#10423) (#10548)

Adds the package file name to exception message in case of JsonException in order to provide clean explanation where to look into.

Fixes #10323

(cherry picked from commit 1ea4cef)

Author: mshabarov

flow-server/src/main/java/com/vaadin/flow/server/frontend/NodeUpdater.java

@@ -37,6 +37,7 @@
 import com.vaadin.flow.server.frontend.scanner.FrontendDependenciesScanner;
 
 import elemental.json.Json;
+import elemental.json.JsonException;
 import elemental.json.JsonObject;
 import elemental.json.JsonValue;
 
@@ -206,7 +207,12 @@ static JsonObject getJsonFileContent(File packageFile) throws IOException {
         if (packageFile.exists()) {
             String fileContent = FileUtils.readFileToString(packageFile,
                     UTF_8.name());
-            jsonContent = Json.parse(fileContent);
+            try {
+                jsonContent = Json.parse(fileContent);
+            } catch (JsonException e) {
+                throw new JsonException(String.format(
+                        "Cannot parse package file '%s'", packageFile));
+            }
         }
         return jsonContent;
     }

flow-server/src/test/java/com/vaadin/flow/server/frontend/NodeUpdaterTest.java

@@ -22,6 +22,9 @@
 import java.util.stream.Collectors;
 import java.util.stream.Stream;
 
+import org.apache.commons.io.FileUtils;
+import org.hamcrest.MatcherAssert;
+import org.hamcrest.core.StringContains;
 import org.junit.Assert;
 import org.junit.Before;
 import org.junit.Rule;
@@ -33,9 +36,11 @@
 import com.vaadin.flow.server.frontend.scanner.FrontendDependencies;
 
 import elemental.json.Json;
+import elemental.json.JsonException;
 import elemental.json.JsonObject;
 import static com.vaadin.flow.server.Constants.COMPATIBILITY_RESOURCES_FRONTEND_DEFAULT;
 import static com.vaadin.flow.server.Constants.RESOURCES_FRONTEND_DEFAULT;
+import static java.nio.charset.StandardCharsets.UTF_8;
 
 public class NodeUpdaterTest {
 
@@ -188,6 +193,24 @@ public void updateDefaultDependencies_newerVersionsAreNotChanged()
                 .getObject(NodeUpdater.DEV_DEPENDENCIES).getString("webpack"));
     }
 
+    @Test
+    public void getJsonFileContent_incorrectPackageJsonContent_throwsExceptionWithFileName()
+            throws IOException {
+        File brokenPackageJsonFile = temporaryFolder
+                .newFile("broken-package.json");
+        FileUtils.writeStringToFile(brokenPackageJsonFile,
+                "{ some broken json ", UTF_8);
+
+        JsonException exception = Assert.assertThrows(JsonException.class,
+                () -> NodeUpdater.getJsonFileContent(brokenPackageJsonFile));
+
+        MatcherAssert.assertThat(exception.getMessage(),
+                StringContains.containsString(
+                        "Cannot parse package file "));
+        MatcherAssert.assertThat(exception.getMessage(),
+                StringContains.containsString("broken-package.json"));
+    }
+
     private String getPolymerVersion(JsonObject object) {
         JsonObject deps = object.get("dependencies");
         String version = deps.getString("@polymer/polymer");