Tab type auto-detection fails when creating a new file #263

Prerequisites

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Description

Tab type auto-detection fails when creating a new .py file. Furthermore, the editor always inserts soft tabs regardless of the Soft Tabs setting (specified in Settings → Editor). It only detects hard tabs correctly if I manually paste a hard tab character and then reopen the file.

Steps to Reproduce

1. Make sure Tab Type is set to auto and Soft Tabs is off (Settings → Editor) and the package-specific settings for language-python are all default

First scenario:

2. Create a new Python source code file
3. Press tab to indent the line

Second scenario:

2. Create a new Python source code file
3. Paste Python code that uses hard tabs
4. Press tab to indent a line

Expected behavior: In the first scenario, I expect the editor to insert a hard tab because there was no other indentation in the document and Soft Tabs is disabled. In the second scenario, I expect the editor to automatically detect that the code uses hard tabs and therefore insert a hard tab when indenting a new line.

Actual behavior: In both scenarios, the editor inserts a soft tab (as if Tab Type was set to soft).

Reproduces how often: Every time.

Versions

$ atom --version
$ apm --version
apm  1.19.0
npm  3.10.10
node 6.9.5 x64
atom 1.28.1
python 2.7.15rc1
git 2.17.1
$ lsb_release -idrc
Distributor ID:	Ubuntu
Description:	Ubuntu 18.04 LTS
Release:	18.04
Codename:	bionic

language-python is on version 0.49.5.

Additional Information

Tab type auto-detection works fine when I disable language-python for Python, or write code in any other language.