fix: surface duplicate VSIX installation error to user notification (#17129)

Follow-up to #16963

- Throw `DuplicateExtensionError` from the resolver instead of silently returning
- Propagate resolver errors through `resolvePlugins` when no plugins were resolved
- Show a localized user-facing notification when a duplicate VSIX install is detected

Author: ndoschek

packages/plugin-ext-vscode/src/node/local-vsix-file-plugin-deployer-resolver.ts

@@ -67,11 +67,11 @@ export class LocalVSIXFilePluginDeployerResolver extends LocalPluginDeployerReso
         const existingPlugins = this.pluginDeployerHandler.getDeployedPluginsById(unversionedId);
         if (existingPlugins.length > 0) {
             const existingVersions = existingPlugins.map(p => p.metadata.model.version);
-            console.log(
-                'Extension ' + unversionedId + ' (version(s): ' + existingVersions.join(', ') + ') is already installed.\n' +
-                'Uninstall the existing extension before installing a new version from VSIX.'
+            const error = new Error(
+                `Extension ${unversionedId} is already installed (version(s): ${existingVersions.join(', ')}).`
             );
-            return;
+            error.name = 'DuplicateExtensionError';
+            throw error;
         }
 
         // Check if the deployment directory already exists on disk

packages/plugin-ext/src/main/node/plugin-deployer-impl.ts

@@ -181,6 +181,7 @@ export class PluginDeployerImpl implements PluginDeployer {
         const hasBeenVisited = (id: string) => visited.has(id) || (visited.add(id), false);
         const pluginsToDeploy = new Map<PluginIdentifiers.VersionedId, PluginDeployerEntry>();
         const unversionedIdsHandled = new Map<PluginIdentifiers.UnversionedId, string[]>();
+        const errors: Error[] = [];
 
         const queue: UnresolvedPluginEntry[] = [...plugins];
         while (queue.length) {
@@ -215,6 +216,7 @@ export class PluginDeployerImpl implements PluginDeployer {
                     }
                 } catch (e) {
                     console.error(`Failed to resolve plugins from '${entry.id}'`, e);
+                    errors.push(e instanceof Error ? e : new Error(String(e)));
                 }
             }));
             queue.length = 0;
@@ -229,6 +231,9 @@ export class PluginDeployerImpl implements PluginDeployer {
                 }
             }
         }
+        if (pluginsToDeploy.size === 0 && errors.length > 0) {
+            throw errors[0];
+        }
         return [...pluginsToDeploy.values()];
     }
 

packages/vsx-registry/src/browser/vsx-extensions-contribution.ts

@@ -266,7 +266,15 @@ export class VSXExtensionsContribution extends AbstractViewContribution<VSXExten
             await this.commandRegistry.executeCommand(VscodeCommands.INSTALL_EXTENSION_FROM_ID_OR_URI.id, fileURI);
             this.messageService.info(nls.localizeByDefault('Completed installing extension.', extensionName));
         } catch (e) {
-            this.messageService.error(nls.localize('theia/vsx-registry/failedInstallingVSIX', 'Failed to install {0} from VSIX.', extensionName));
+            if (e instanceof Error && e.name === 'DuplicateExtensionError') {
+                this.messageService.error(
+                    nls.localize('theia/vsx-registry/duplicateVSIX',
+                        'Failed to install {0} from VSIX. The extension is already installed. Uninstall the existing extension before installing a new version from VSIX.',
+                        extensionName)
+                );
+            } else {
+                this.messageService.error(nls.localize('theia/vsx-registry/failedInstallingVSIX', 'Failed to install {0} from VSIX.', extensionName));
+            }
             console.warn(e);
         }
     }