A simple way to remove would be to just do conda config --remove channels defaults

Could also override the condarc with the channels you want

Hi @jrbourbeau

So we should be using /Users/runner/.condarc and not miniconda3/.condarc it seems

We will take a look

Ran into this as well in issue ( conda-forge/clangdev-feedstock#166 ), which led to a bit of a confusing linking error

I think I have the same issue, although I did not use an environment file.

I can verify that with this workflow:

name: Setup Miniconda

on:
  repository_dispatch:
    types:
      - setup-miniconda

jobs:
  setup:
    runs-on: "macos-latest"
    name: Setup
    defaults:
      run:
        shell: bash -l {0}
    steps:
    - uses: conda-incubator/setup-miniconda@v2
      with:
        miniconda-version: "py38_4.8.3"
        python-version: "3.8"
        channels: conda-forge
    # - run: conda config --remove channels defaults
    - run: conda config --show channels
    - run: cat /Users/runner/.condarc

the defaults channel is still used, and the contents of /Users/runner/.condarc are:

notify_outdated_conda: false
pkgs_dirs:
  - /Users/runner/conda_pkgs_dir
channels:
  - conda-forge
  - defaults
auto_activate_base: true
auto_update_conda: false
always_yes: true
changeps1: false

Also, using the workaround suggested by @jakirkham works.

Something else worth trying might be adding nodefaults to the channels

This is interesting behavior of Conda, to always add defaults unless channels is already defined:

echo "" > test.condarc
conda config --add channels conda-forge --file test.condarc
cat test.condarc
# channels:
#   - conda-forge
#   - defaults

echo "channels: []" > test.condarc
conda config --add channels conda-forge --file test.condarc
cat test.condarc
# channels:
#   - conda-forge

Something else worth trying might be adding nodefaults to the channels

This is even done in the source code for example 6 (although that's not what's shown on the readme); unfortunately all this does is add - nodefaults to the channel list:

Log source for image: https://github.com/conda-incubator/setup-miniconda/actions/runs/10551479166/job/29228977318

Although this doesn't seem like what's intended from the example, it is intelligible from the source: