We have to read through #1026 (the PR that added tabs support) again, because as far as I remember all of this was discussed back then.

When using spaces, Prettier indents with 2 spaces + 1 indent level. When using tabs, there are three ways to go:

• Indent with one tab.
• Indent with two tabs.
• Indent with 2 spaces + 1 tab.

As far as I remember, all of those were discussed with pros and cons, but I don't have the time right now to dig into it.

• before
  • let tabWidth = 2
    • <tab><2 space><tab><2 space> -> <tab><tab><tab><tab>
    • <tab><4 space><tab><2 space> -> <tab><tab><tab><tab>
  • let tabWidth = 4
    • <tab><2 space><tab><2 space> -> <tab><tab><tab><tab>
    • <tab><4 space><tab><2 space> -> <tab><tab><tab><tab>
• after
  • let tabWidth = 2
    • <tab><2 space><tab><2 space> -> <tab><tab><tab><2 space>
    • <tab><4 space><tab><2 space> -> <tab><tab><tab><tab><2 space>
  • let tabWidth = 4
    • <tab><2 space><tab><2 space> -> <tab><tab><2 space>
    • <tab><4 space><tab><2 space> -> <tab><tab><tab><2 space>

Since the change in the 3rd screenshot is same as the current { useTabs: false, tabWidth: 4 } result, I think it's not a regression... right?

Prettier 1.8.2
Playground link

--tab-width 4

Input:

aaaaaaaaaaaaaaa ? bbbbbbbbbbbbbbbbbb : ccccccccccccccc ? ddddddddddddddd : eeeeeeeeeeeeeee ? fffffffffffffff : gggggggggggggggg

Output:

aaaaaaaaaaaaaaa
    ? bbbbbbbbbbbbbbbbbb
    : ccccccccccccccc
      ? ddddddddddddddd
      : eeeeeeeeeeeeeee ? fffffffffffffff : gggggggggggggggg;

Rewrite in #3745.