[plug-in] Need to implement "files.associations" configuration property

[vrubezhny]

https://code.visualstudio.com/docs/languages/identifiers

Configuration example:

"contributes": {
    "configurationDefaults": {
	'id': 'files',
	'type': 'object',
	'properties': {
		'files.associations': {
			'type': 'object',
			'markdownDescription': nls.localize('associations', "Configure file associations to languages (e.g. `\"*.extension\": \"html\"`). These have precedence over the default associations of the languages installed."),
		}
	}
}

https://github.com/Microsoft/vscode/blob/master/src/vs/platform/files/common/files.ts#L681

export interface IFilesConfiguration {
	files: {
		associations: { [filepattern: string]: string };
		exclude: glob.IExpression;
		watcherExclude: { [filepattern: string]: boolean };
		encoding: string;
		autoGuessEncoding: boolean;
		defaultLanguage: string;
		trimTrailingWhitespace: boolean;
		autoSave: string;
		autoSaveDelay: number;
		eol: string;
		hotExit: string;
		useExperimentalFileWatcher: boolean;
	};
}

It is impossible to install intelephense extension as Theia extension plugin because it requires a defined object (even an empty one is valid) to be returned when it requests for the associations preference in section files, otherwise, the following code (that is invoked when it's being activated):

vscode_1.workspace.getConfiguration('files').get('associations');

results into the following exception and failure:

PLUGIN_HOST(22186): initializing(/home/jeremy/projects/che/source/theia-ide/theia/packages/plugin-ext-vscode/lib/node/plugin-vscode-init.js)
PLUGIN_HOST(22186): PluginManagerExtImpl/loadPlugin(/tmp/vscode-unpacked/bmewburn.vscode-intelephense-client-1.0.8.vsix/extension/out/src/extension)

root INFO [nsfw-watcher: 22228] Started watching: /home/jeremy/projects/che/theia-runtime-workspace/.theia/phptest.php
root ERROR [hosted-plugin: 22186] (node:22186) UnhandledPromiseRejectionWarning: TypeError: Cannot convert undefined or null to object
    at Function.keys (<anonymous>)
    at workspaceFilesIncludeGlob (/tmp/vscode-unpacked/bmewburn.vscode-intelephense-client-1.0.8.vsix/extension/out/src/extension.js:125:31)
    at /tmp/vscode-unpacked/bmewburn.vscode-intelephense-client-1.0.8.vsix/extension/out/src/extension.js:74:72
    at Generator.next (<anonymous>)
    at /tmp/vscode-unpacked/bmewburn.vscode-intelephense-client-1.0.8.vsix/extension/out/src/extension.js:10:71
    at new Promise (<anonymous>)
    at __awaiter (/tmp/vscode-unpacked/bmewburn.vscode-intelephense-client-1.0.8.vsix/extension/out/src/extension.js:6:12)
    at activate (/tmp/vscode-unpacked/bmewburn.vscode-intelephense-client-1.0.8.vsix/extension/out/src/extension.js:29:12)
    at PluginManagerExtImpl.startPlugin (/home/jeremy/projects/che/source/theia-ide/theia/packages/plugin-ext/lib/plugin/plugin-manager.js:172:73)
    at PluginManagerExtImpl.$init (/home/jeremy/projects/che/source/theia-ide/theia/packages/plugin-ext/lib/plugin/plugin-manager.js:126:26)

root ERROR [hosted-plugin: 22186] (node:22186) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
(node:22186) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

In order to run the intelephense in my local environment I've workarounded this issue with the following change, but for sure it can't be used in production:

$ git diff packages/plugin-ext/src/plugin/preference-registry.ts
diff --git a/packages/plugin-ext/src/plugin/preference-registry.ts b/packages/plugin-ext/src/plugin/preference-registry.ts
index fa74a71b..cb943256 100644
--- a/packages/plugin-ext/src/plugin/preference-registry.ts
+++ b/packages/plugin-ext/src/plugin/preference-registry.ts
@@ -100,7 +100,7 @@ export class PreferenceRegistryExtImpl implements PreferenceRegistryExt {
             get: <T>(key: string, defaultValue?: T) => {
                 const result = lookUp(preferences, key);
                 if (typeof result === 'undefined') {
-                    return defaultValue;
+                    return defaultValue ? defaultValue : {};
                 } else {
                     let clonedConfig: any = undefined;
                     const cloneOnWriteProxy = (target: any, accessor: string): any => {

Reference issues:
eclipse-che/che#12796
eclipse-che/che#12797
#1106
#4716

[tsmaeder]

"files.associations" is documented as a VS Code preference here: https://code.visualstudio.com/docs/getstarted/settings

[tsmaeder]

I see two problems here:

1. There is no default preference "files.associations" in Theia, so I guess we should add it.
2. What preference in Theia is used instead to associate files with languages? We need to do some adaptation in order to make this work.

[tsmaeder]

In a first step, let's add the preference key and find out whether there is more work that we need to do.

[akosyakov]

I believe it was not fixed and an incomplete solution was merged on master, i.e. there is a confusing preference now which does not change anything. This preference should affect editors in order a PR to be merged. @tolusha Please revert if you are not going to submit the rest today and reopen with complete solution.

[tolusha]

@akosyakov
Sorry, I might misunderstood something.
What does complete solution means?

[benoitf]

AFAIK step1 is done as announced. Also it's great to see that php VS Code extension could run as well.
IMHO there is no clear definition of "incomplete" or "done". Master should allow multiple-steps work as long as it doesn't break features.

[akosyakov]

@benoitf @tolusha #4716 it is a new bug introduced by #4713, it is a definition of not done to me

[tsmaeder]

To quote myself (hehe):

In a first step, let's add the preference key and find out whether there is more work that we need to do.

So is there more to do, @tolusha?

[tsmaeder]

@benoitf @tolusha #4716 it is a new bug introduced by #4713, it is a definition of not done to me

I would argue that this is not really a regression, since the preference was never honored anyway, correct?

[akosyakov]

I would argue that this is not really a regression, since the preference was never honored anyway, correct?

it is not a regression, true, just a new bug, before Theia does not provide this preference in UI anywhere, now it does, but does not support

[tolusha]

How VS Code resolves language

There is a single location [1] where all associations stored. They come either from language registry [2] or from files.associations configuration property [3]. Language resolving comes to mimetype guessing [4] using registered associations where files.associations are prioritized.

How Theia resolves language

Basically it works the same. Through [5] it comes to [4] as well. So, basically adding files.associations to the file system preferences [6] and implementing something like [3] should help.

[1] https://github.com/Microsoft/vscode/blob/master/src/vs/base/common/mime.ts#L39
[2] https://github.com/Microsoft/vscode/blob/master/src/vs/editor/common/services/languagesRegistry.ts#L32
[3] https://github.com/Microsoft/vscode/blob/master/src/vs/workbench/services/mode/common/workbenchModeService.ts#L169
[4] https://github.com/Microsoft/vscode/blob/master/src/vs/base/common/mime.ts#L109
[5] https://github.com/theia-ide/theia/blob/master/packages/monaco/src/browser/monaco-editor-model.ts#L86
[6] https://github.com/theia-ide/theia/blob/master/packages/filesystem/src/browser/filesystem-preferences.ts#L27

[akosyakov]

There should not be dependencies between editor and filesystem extensions. It could be a tricky part. I think you can go ahead and implement, and then we can refactor it a bit together during review to break a dependency if it appears.

[tsmaeder]

I'm not sure fixing this would introduce such a dependency. @tolusha could you explain how your fix would look? It's not obvious to me from looking at the references sources.

[tolusha]

@tsmaeder
From my understanding we need entity to track files.associations changes and respectively update mimetype resolver [1]

[1] https://github.com/Microsoft/vscode/blob/master/src/vs/base/common/mime.ts#L109

[tsmaeder]

That points to VSCode. Where does this code live in Theia, @tolusha ?

[akosyakov]

It should already be in Monaco. It would be nice introduce something like MimeService stub class in core extension, implement and rebind in Monaco extension (with exposing minimal API surface from mime.ts), and use in the filesystem extension.