What is the difference between dependencies and extra-dependencies in inherited environments?

[ARKAD97]

I tried on small project:

dependencies = [
  "pandas",
  "black"
]

[tool.hatch.envs.env1]
dependencies = [
  "polars",
  "fire"
]

and via:

hatch -e env1 shell
pip freeze

I see that all "pandas", "black", "polars", "fire" are installed. Which means dependencies option doesn't overwrites dependencies listed in parent's environment.

Documentation says:
If you define environments with dependencies that only slightly differ from their inherited environments, you can use the extra-dependencies option to avoid redeclaring the dependencies option.
What does mean "only slightly differ", what are the consequences of "redeclaring the dependecies option" in child environment?

My guess is that extra-dependencies is a synonym for dependencies which was added later to avoid confusion. Am I correct?

Thank you for your time!

[ofek]

We would need to see the full example; it looks like the first line or more is missing.

[ARKAD97]

It is just default project generated by hatch with little modifications.
I created it just to try out hatch and figure out difference between dependencies and extra-dependencies in child environments:

[build-system]
requires = ["hatchling"]
build-backend = "hatchling.build"

[project]
name = "test-project"
dynamic = ["version"]
description = ''
readme = "README.md"
requires-python = ">=3.11"
license = "MIT"
keywords = []
authors = [
  { name = "U.N. Owen", email = "[email protected]" },
]
classifiers = [
  "Development Status :: 4 - Beta",
  "Programming Language :: Python",
  "Programming Language :: Python :: 3.11",
  "Programming Language :: Python :: 3.12",
  "Programming Language :: Python :: 3.13",
  "Programming Language :: Python :: Implementation :: CPython",
  "Programming Language :: Python :: Implementation :: PyPy",
]
dependencies = [
  "pandas",
  "black"
]

[tool.hatch.envs.env1]
extra-dependencies = [
  "polars",
  "fire"
]

[project.urls]
Documentation = "https://github.com/U.N. Owen/test-project#readme"
Issues = "https://github.com/U.N. Owen/test-project/issues"
Source = "https://github.com/U.N. Owen/test-project"

[tool.hatch.version]
path = "src/test_project/__about__.py"

[tool.hatch.envs.types]
extra-dependencies = [
  "mypy>=1.0.0",
]
[tool.hatch.envs.types.scripts]
check = "mypy --install-types --non-interactive {args:src/test_project tests}"

[tool.coverage.run]
source_pkgs = ["test_project", "tests"]
branch = true
parallel = true
omit = [
  "src/test_project/__about__.py",
]

[tool.coverage.paths]
test_project = ["src/test_project", "*/test-project/src/test_project"]
tests = ["tests", "*/test-project/tests"]

[tool.coverage.report]
exclude_lines = [
  "no cov",
  "if __name__ == .__main__.:",
  "if TYPE_CHECKING:",
]

[ofek]

Project dependencies are an entirely different concept; those will always be included in environments by virtue of the installation which you can disable with the skip-install option. What you're referring to is environment dependencies and inheritance.

[ARKAD97]

I see now.

I thought that project dependencies are dependencies of the default environment, which turned to be false.