### Discussed in https://github.com/apache/airflow/discussions/36076

<div type='discussions-op-text'>

<sup>Originally posted by **timc** December  5, 2023</sup>
### Apache Airflow version

2.7.3

### What happened

When creating a virtual env task and passing in a requirements file like this:

`@task.virtualenv(
            use_dill=True,
            system_site_packages=False,
            requirements='requirements.txt')`

The result is that the contents of the requirements file using to populate the venv is

requirements.txt

Which is wrong. And you get this:

[2023-12-05, 12:33:06 UTC] {{process_utils.py:181}} INFO - Executing cmd: python3 /usr/local/***/.local/lib/python3.10/site-packages/virtualenv /tmp/venv3cdlqjlq
[2023-12-05, 12:33:06 UTC] {{process_utils.py:185}} INFO - Output:
[2023-12-05, 12:33:07 UTC] {{process_utils.py:189}} INFO - created virtual environment CPython3.10.9.final.0-64 in 397ms
[2023-12-05, 12:33:07 UTC] {{process_utils.py:189}} INFO -   creator CPython3Posix(dest=/tmp/venv3cdlqjlq, clear=False, no_vcs_ignore=False, global=False)
[2023-12-05, 12:33:07 UTC] {{process_utils.py:189}} INFO -   seeder FromAppData(download=False, pip=bundle, setuptools=bundle, wheel=bundle, via=copy, app_data_dir=/usr/local/***/.local/share/virtualenv)
[2023-12-05, 12:33:07 UTC] {{process_utils.py:189}} INFO -     added seed packages: pip==23.3.1, setuptools==69.0.2, wheel==0.42.0
[2023-12-05, 12:33:07 UTC] {{process_utils.py:189}} INFO -   activators BashActivator,CShellActivator,FishActivator,NushellActivator,PowerShellActivator,PythonActivator
[2023-12-05, 12:33:07 UTC] {{process_utils.py:181}} INFO - Executing cmd: /tmp/venv3cdlqjlq/bin/pip install -r /tmp/venv3cdlqjlq/requirements.txt
[2023-12-05, 12:33:07 UTC] {{process_utils.py:185}} INFO - Output:
[2023-12-05, 12:33:09 UTC] {{process_utils.py:189}} INFO - ERROR: Could not find a version that satisfies the requirement requirements.txt (from versions: none)
[2023-12-05, 12:33:09 UTC] {{process_utils.py:189}} INFO - HINT: You are attempting to install a package literally named "requirements.txt" (which cannot exist). Consider using the '-r' flag to install the packages listed in requirements.txt
[2023-12-05, 12:33:09 UTC] {{process_utils.py:189}} INFO - ERROR: No matching distribution found for requirements.txt
[2023-12-05, 12:33:09 UTC] {{taskinstance.py:1824}} ERROR - Task failed with exception

The issue appears to be that the requirements parameter is added to a list on construction of the operator so the templating never happens.

### What you think should happen instead

The provided requirements file should be used in the pip command to set up the venv.

### How to reproduce

Create a dag:

```
from datetime import datetime
from airflow.decorators import dag, task

 @dag(schedule_interval=None, start_date=datetime(2021, 1, 1), catchup=False, tags=['example']) 
def virtualenv_task():
    @task.virtualenv(
        use_dill=True,
        system_site_packages=False,
        requirements='requirements.txt',
    )
    def extract():
        import pandas 
        x = pandas.DataFrame()

    extract()

dag = virtualenv_task()
```
And a requirements.txt file

```
pandas
```

Run AirFlow

### Operating System

Ubuntu 23.04

### Versions of Apache Airflow Providers

apache-airflow-providers-amazon==8.2.0
apache-airflow-providers-celery==3.2.1
apache-airflow-providers-common-sql==1.5.2
apache-airflow-providers-ftp==3.4.2
apache-airflow-providers-http==4.4.2
apache-airflow-providers-imap==3.2.2
apache-airflow-providers-postgres==5.5.1
apache-airflow-providers-sqlite==3.4.2

### Deployment

Docker-Compose

### Deployment details

_No response_

### Anything else

Everytime.

### Are you willing to submit PR?

- [ ] Yes I am willing to submit a PR!

### Code of Conduct

- [X] I agree to follow this project's [Code of Conduct](https://github.com/apache/airflow/blob/main/CODE_OF_CONDUCT.md)
</div>
#
#
#
from __future__ import annotations
import datetime
import subprocess
import venv
from datetime import timedelta
from pathlib import Path
from subprocess import CalledProcessError
from tempfile import TemporaryDirectory
import pytest
from airflow.decorators import setup, task, teardown
from airflow.utils import timezone
pytestmark = pytest.mark.db_test
DEFAULT_DATE = timezone.datetime(2016, 1, 1)
END_DATE = timezone.datetime(2016, 1, 2)
INTERVAL = timedelta(hours=12)
FROZEN_NOW = timezone.datetime(2016, 1, 2, 12, 1, 1)
TI_CONTEXT_ENV_VARS = [
    "AIRFLOW_CTX_DAG_ID",
    "AIRFLOW_CTX_TASK_ID",
    "AIRFLOW_CTX_EXECUTION_DATE",
    "AIRFLOW_CTX_DAG_RUN_ID",
]
@pytest.fixture()
def venv_python():