[BUG] npm ls --prod is not omitting dev deps of workspaces

[ruyadorno]

Is there an existing issue for this?

• I have searched the existing issues

Current Behavior

Running npm ls --production is not omitting dev deps of child workspaces, e.g:

# Given a workspace structure:
.
├── a
│   └── package.json (devDependencies: abbrev@^1.1.1)
├── b
│   └── package.json
└── package.json

# Running default list:
$ npm ls
test-ls-workspaces-dev@1.0.0 <path>/test-ls-workspaces-dev
├─┬ a@1.0.0 -> ./a
│ └── abbrev@1.1.1
└── b@1.0.0 -> ./b

# Running prod-only list:
$ npm ls --prod
test-ls-workspaces-dev@1.0.0 <path>/test-ls-workspaces-dev
├─┬ a@1.0.0 -> ./a
│ └── abbrev@1.1.1
└── b@1.0.0 -> ./b

Expected Behavior

# Given a workspace structure:
.
├── a
│   └── package.json (devDependencies: abbrev@^1.1.1)
├── b
│   └── package.json
└── package.json

# Running prod-only list:
$ npm ls --prod
test-ls-workspaces-dev@1.0.0 <path>/test-ls-workspaces-dev
├── a@1.0.0 -> ./a
└── b@1.0.0 -> ./b

Steps To Reproduce

1. In an properly configured workspaces project
2. Run npm ls --prod
3. Should not be seeing dev deps of child workspaces

Environment

• Node: v16.3.0
• npm: v7.16.0