Checklist

• I added a descriptive title
• I searched open reports and couldn't find a duplicate

What happened?

conda create and install commands support a --file argument which is a list of files to install. Files can either be explicit files or regular text files. If there is a mix of --files that specify regular packages and explicit package then this will produce a ParseError. For example, consider the following two environment files:

env1.txt (explicit file)

@EXPLICIT
https://repo.anaconda.com/pkgs/main/linux-64/_libgcc_mutex-0.1-main.conda
https://repo.anaconda.com/pkgs/main/linux-64/ca-certificates-2025.2.25-h06a4308_0.conda

env2.txt (regular text file)

Running a conda create against these files individually works. Providing both files as arguments produces an error:

$ conda create -n testenv-mixed --file env1.txt --file env2.txt 

ParseError: Could not parse explicit URL: file:///home/sophia/projects/conda/numpy

It is correct to raise an error for this situation, but it would be helpful if the error more accurately described what is going wrong and how to fix it. For example, it would be better for the result to be something like

$ conda create -n testenv-mixed --file env1.txt --file env2.txt 

CondaError: can not mix `file` types

env1.txt is found to be an explicit type file
env2.txt is found to be requirements.txt type file

Checklist

• Ensure conda does not allow for mixing input file types #14725
• Add environment spec plugin for explicit input file types conda-planning#47