[preferences] fix indentation when updating preferences through the tree

[vince-fugnitto]

What it does

Fixes #5052

Fixes the inconsistent formatting when attempting to update/set preferences using the preferences-tree widget. Since the formatting options passed to jsoncparser were hardcoded, the formatting would be inconsistent with whichever formatting the editor currently has:

theia/packages/preferences/src/browser/abstract-resource-preference-provider.ts

Line 107 in 928e1e0

const formattingOptions = { tabSize: 3, insertSpaces: true, eol: '' };

In order to fix the issue, the following method detectIndentation was implemented which attempts to determine the tabSize and indentType (insertSpaces) directly from the TextEditorDocument of the settings.json file in question. This is done in order to get a more accurate representation of the actual formatting present in the file.

The following is the before and after when adding a new preference terminal.enableCopy through the preferences-tree:

Before (using tabSize=8)	After (using tabSize=8)

How to test

1. attempt to add preferences through the preferences-tree widget
2. update the tabSize using the statusbar and format the document accordingly (repeat step 1)
3. update the indentType (spaces or tabs) using the statusbar, format the document accordingly (repeat step 1)
4. repeat step 1 using both user and workspace files

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: vince-fugnitto vincent.fugnitto@ericsson.com

[lmcbout]

Test the format on Ubuntu 16.04 and Chrome: works fine

[vince-fugnitto]

@akosyakov I noticed a potential issue with the preferences for languages. During testing, I updated the global preference editor.insertSpaces to false, but it did not look to apply to the JSON language when getting the preference. Is this by design?

I had to do the following as a workaround:

"[json]": {
    "editor.insertSpaces": false
}

Also, not sure if we should use [json] or [jsonc] when checking for preferences.

[akosyakov]

@vince-fugnitto I think jsonc should be proper for preferences.

[akosyakov]

code-wise it looks good to me

[vince-fugnitto]

@lmcbout if you get a chance, can you please re-test the pull request?
The overall strategy has been changed and simplified.

[lmcbout]

Tested with @vince-fugnitto not perfect, but OK

[vince-fugnitto]

Tested with @vince-fugnitto not perfect, but OK

@lmcbout I completely understand, the pull request becomes best effort when the settings document is not properly formatted or is formatted inconsistently (different tabSize and indentation throughout the document).

When the document is properly formatted, inserting preferences from the preferences-tree is more consistent. Overall, the pull request improves upon the original implementation which used hard coded values and would always format inconsistently.

Perhaps we can improve the pull request further in the future, but I am unsure what an appropriate strategy would be when working with un-formatted documents.