Handle pref display without plugins

[colin-grant-work]

What it does

A bug was discovered by a user of the Yo Theia Extension Generator in which the preference widget was not displaying preferences unless an extension with plugin support was included in the dependencies.

The basic problem was that the PreferenceTreeGenerator was waiting for an event from the PreferenceSchemaProvider before initializing its tree.

theia/packages/preferences/src/browser/util/preference-tree-generator.ts

Lines 32 to 35 in a8dec8d

	@postConstruct()
	protected init(): void {
	this.schemaProvider.onDidPreferenceSchemaChanged(() => this.handleChangedSchema());
	}

That event is only fired when plugins call the setSchema method:

theia/packages/core/src/browser/preferences/preference-contribution.ts

Lines 308 to 323 in a8dec8d

	setSchema(schema: PreferenceSchema): Disposable {
	const changes = this.doSetSchema(schema);
	if (!changes.length) {
	return Disposable.NULL;
	}
	this.fireDidPreferenceSchemaChanged();
	this.emitPreferencesChangedEvent(changes);
	return Disposable.create(() => {
	const inverseChanges = this.doUnsetSchema(changes);
	if (!inverseChanges.length) {
	return;
	}
	this.fireDidPreferenceSchemaChanged();
	this.emitPreferencesChangedEvent(inverseChanges);
	});
	}

Internal preference contributions only call doSetSchema, which does not fire any events. I believe this behavior is correct: the schema hasn't changed, but only been initialized.

theia/packages/core/src/browser/preferences/preference-contribution.ts

Lines 126 to 128 in a8dec8d

	this.preferenceContributions.getContributions().forEach(contrib => {
	this.doSetSchema(contrib.schema);
	});

This PR modifies the behavior of the PreferenceTreeGenerator to generate a tree when the PreferenceSchemaProvider is ready (after all internal preference contributions have been processed) without waiting for an onSchemaChanged event.

How to test

1. Modify the electron or browser package.json to have only these Theia packages as dependencies:

  "dependencies": {
    "@theia/core": "1.12.0",
    "@theia/editor": "1.12.0",
    "@theia/electron": "1.12.0",
    "@theia/filesystem": "1.12.0",
    "@theia/markers": "1.12.0",
    "@theia/messages": "1.12.0",
    "@theia/monaco": "1.12.0",
    "@theia/navigator": "1.12.0",
    "@theia/preferences": "1.12.0",
    "@theia/process": "1.12.0",
    "@theia/terminal": "1.12.0",
    "@theia/workspace": "1.12.0",
  },

2. Build and start the application, and open the preferences view (ctrl + ,)
3. Observe that the preferences are populated.

Review checklist

• as an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• as a reviewer, I agree to behave in accordance with the review guidelines

Signed-off-by: Colin Grant [email protected]

[vince-fugnitto]

I confirmed that the pull-request fixes the issue 👍

[jwebstar]

I'm seeing this behaviour again in 1.15. When I generate a new extension with theia extension generator preferences are listed. But if I change the package.json theia dependencies from 'latest' to 'next' there are no preferences listed in the browser or Electron. Adding the dependency "@theia/external-terminal": "next", to Electron brings back the preferences in Electron.

[colin-grant-work]

@jwebstar, thanks for bringing this to my attention. I had a couple of lines of work running in parallel, and it's possible that a later merge ended up missing this fix. I'll check into it.