--no-index not respected when --requirement file contains --index-url

[vanschelven]

Description

The behavior of index-url, when used in combination with --no-index, is inconsistent between specifiying it on the command line and in a requirements.txt-like file. Proof:

$ pip install --index-url https://pypi.org/simple --no-index boto3
ERROR: Could not find a version that satisfies the requirement boto3 (from versions: none)
ERROR: No matching distribution found for boto3

$ cat requirements.txt 
--index-url https://pypi.org/simple

$ pip install -i https://pypi.org/simple --no-index -r requirements.txt boto3
Collecting boto3
  Downloading boto3-1.24.33-py3-none-any.whl (132 kB)
     ━━━━━━━━━━━
ERROR: Operation cancelled by user

The same is true for --extra-index-url

Expected behavior

No response

pip version

22.1.2

Python version

3.9

OS

Ubuntu

How to Reproduce

.

Output

No response

Code of Conduct

• I agree to follow the PSF Code of Conduct.

[vanschelven]

The explanation seems to be that there's some code to deal with the command-line as a special-case, but this code is not replicated for the handling of options when part of requirements.txt.

[vanschelven]

The code to deal with the command-line as a special case mentioned above is specific to --index-url (not present for extra-index-url) but yet another special case is present that makes it so that extra-index-url has similar inconsistent behavior between command-line and --requirements usage: https://github.com/pypa/pip/blob/main/src/pip/_internal/index/collector.py#L553