Redhat XML plugin error (on 1.65): Activating plugin 'XML' failed: Cannot set properties of undefined (setting 'file')

[safisa]

Bug Description:

Hi,
When upgraded from Theia 1.64 to 1.65, I got this error on page load (as a notification pop-up):
Activating plugin 'XML' failed: Cannot set properties of undefined (setting 'file')

And in the browser console logs:

2025-10-03T10:22:23.378Z root ERROR [9a27bbe6-5a5e-43eb-b7ec-7e2f7a59b703][redhat.vscode-xml]: Failed to load 'configuration' contribution. Error: Property with id 'redhat.telemetry.enabled' already exists
    at PreferenceSchemaServiceImpl.addSchema (http://localhost:3001/bundle.js:407618:23)
    at http://localhost:3001/packages_plugin-ext_lib_hosted_browser_hosted-plugin_js.js:8274:87
    at pushContribution (http://localhost:3001/packages_plugin-ext_lib_hosted_browser_hosted-plugin_js.js:8265:32)
    at PluginContributionHandler.handleContributions (http://localhost:3001/packages_plugin-ext_lib_hosted_browser_hosted-plugin_js.js:8274:17)
    at HostedPluginSupport.handleContributions (http://localhost:3001/packages_plugin-ext_lib_hosted_browser_hosted-plugin_js.js:723:41)
    at HostedPluginSupport.loadContributions (http://localhost:3001/packages_plugin-ext_lib_hosted_browser_hosted-plugin_js.js:1476:41)
    at HostedPluginSupport.doLoad (http://localhost:3001/packages_plugin-ext_lib_hosted_browser_hosted-plugin_js.js:1361:42)
    at async ProgressService.withProgress (http://localhost:3001/bundle.js:408571:20)
    at async http://localhost:3001/packages_plugin-ext_lib_hosted_browser_hosted-plugin_js.js:1317:17

2025-10-03T10:22:25.151Z plugin-manager ERROR Activating plugin 'XML' failed: TypeError: Cannot set properties of undefined (setting 'file')
    at t.getXMLSettings (/Users/safi/dev/theia/plugins/vscode.xml-redhat/extension/dist/extension.js:1:345027)
    at /Users/safi/dev/theia/plugins/vscode.xml-redhat/extension/dist/extension.js:1:302041
    at /Users/safi/dev/theia/plugins/vscode.xml-redhat/extension/dist/extension.js:1:302668
    at Generator.next (<anonymous>)
    at /Users/safi/dev/theia/plugins/vscode.xml-redhat/extension/dist/extension.js:1:301302
    at new Promise (<anonymous>)
    at r (/Users/safi/dev/theia/plugins/vscode.xml-redhat/extension/dist/extension.js:1:301047)
    at t.startLanguageClient (/Users/safi/dev/theia/plugins/vscode.xml-redhat/extension/dist/extension.js:1:301851)
    at /Users/safi/dev/theia/plugins/vscode.xml-redhat/extension/dist/extension.js:1:317609
    at Generator.next (<anonymous>)

2025-10-03T10:22:25.995Z plugin-host ERROR Promise rejection not handled in one second: Error: Cannot set configuration for unknown language svg , reason: Error: Cannot set configuration for unknown language svg

2025-10-03T10:22:25.995Z plugin-host ERROR With stack trace: Error: Cannot set configuration for unknown language svg
    at Object.setLanguageConfiguration (standaloneLanguages.ts:97:9)
    at LanguagesMainPluginMetrics.$setLanguageConfiguration (languages-main.ts:172:48)
    at RPCProtocolImpl.handleRequest (rpc-protocol.ts:108:31)
    at RpcProtocol.requestHandler (rpc-protocol.ts:88:89)
    at RpcProtocol.handleRequest (rpc-protocol.ts:232:39)
    at RpcProtocol.handleMessage (rpc-protocol.ts:104:26)
    at rpc-protocol.ts:88:66
    at event.ts:176:42
    at CallbackList.invoke (event.ts:184:26)
    at Emitter.fire (event.ts:327:36)

Steps to Reproduce:

1. Install Redhat XML plugin
2. Open an XML file in the browser app
3. You will see the activation notification error
4. Open console logs from dev-tools, you will see the above errors

Additional Information

• Operating System: Mac - chrome
• Theia Version: 1.65

[safisa]

Hi @tsmaeder @ndoschek ,
I believe the changes in the PR #16017 are the cause of this issue.

The addSchema method in PreferenceSchemaServiceImpl (@theia/core/lib/common/preferences/preference-schema-service) throws an error if a property ID already exists. Once I have overridden this method and just continue instead of throwing an error, it fixes the issue:

@injectable()
export class CustomPreferenceSchemaServiceImpl extends PreferenceSchemaServiceImpl {

    override addSchema(schema: PreferenceSchema): Disposable {
        //return super.addSchema(schema);

        this.schemas.add(schema);

        for (const [key, property] of Object.entries(schema.properties)) {
            if (this.properties.has(key)) {
                //throw new Error(`Property with id '${key}' already exists`);
                console.warn(`Property with id '${key}' already exists`);
                continue;
            }

            if (property.scope === undefined) {
                property.scope = schema.scope;
            }

            if (property.overridable === undefined) {
                property.overridable = schema.defaultOverridable;
            }

            this.properties.set(key, property);
            ///@ts-ignore
            this.setJSONSchemasProperty(key, property);
            if (property.default !== undefined) {
                this.defaultValueChangedEmitter.fire(this.changeFor(key, undefined, this.defaultOverrides.get(key), undefined, property.default!));
            }

        }

        this.schemaChangedEmitter.fire();

        return Disposable.create(() => {
            if (this.schemas.delete(schema)) {
                for (const [key, property] of Object.entries(schema.properties)) {
                    ///@ts-ignore
                    this.deleteFromJSONSchemas(key, property);
                    this.properties.delete(key);
                    const overrides = this.defaultOverrides.get(key);

                    ///@ts-ignore
                    const baseOverride = overrides?.get(NO_OVERRIDE);
                    if (baseOverride !== undefined) {
                        this.defaultValueChangedEmitter.fire(this.changeFor(key, undefined, overrides, baseOverride, undefined));
                    } else if (property.default !== undefined) {
                        this.defaultValueChangedEmitter.fire(this.changeFor(key, undefined, overrides, property.default, undefined));
                    }
                    if (overrides) {
                        for (const [overrideKey, value] of overrides) {
                            if (typeof overrideKey === 'string') {
                                this.defaultValueChangedEmitter.fire(this.changeFor(key, overrideKey, overrides, value[0][1], undefined));
                            }
                        }
                    }
                }

                this.schemaChangedEmitter.fire();
            }
        });
    }
}

I had to add these ///@ts-ignore for private methods and constants, because they are not exposed as protected!!!
This fix also resolved a similar issue, where I had the same setting in my vscode plugin and in my Theia extension.

I think this needs to be fixed on the Theia side and not as I did in my extension.

Thanks