# Environment configuration

-----

All environments are defined as sections within the `tool.hatch.envs` table.

```toml config-example
[tool.hatch.envs.<ENV_NAME>]
```

The [storage location](../hatch.md#environments) for environments is completely configurable.

Unless an environment is explicitly selected on the command line, the `default` environment will be used. The [type](#type) of this environment defaults to `virtual`.

!!! info
    Environments prefixed by `hatch-` are used for special purposes e.g. [testing](../internal/testing.md).

## Inheritance

All environments inherit from the environment defined by its `template` option, which defaults to `default`.

So for the following configuration:

```toml config-example
[tool.hatch.envs.foo]
type = "baz"
skip-install = true

[tool.hatch.envs.bar]
template = "foo"
skip-install = false
```

the environment `bar` will be of type `baz` with `skip-install` set to `false`.

!!! note
    Environments do not inherit [matrices](advanced.md#matrix).

### Self-referential environments

You can disable inheritance by setting `template` to the environment's own name:

```toml config-example
[tool.hatch.envs.foo]
template = "foo"
```

### Detached environments

A common use case is standalone environments that do not require inheritance nor the installation of the project, such as for linting or sometimes building documentation. Enabling the `detached` option will make the environment [self-referential](#self-referential-environments) and will [skip project installation](#skip-install):

```toml config-example
[tool.hatch.envs.lint]
detached = true
```

## Dependencies

You can install [dependencies](../dependency.md) in addition to the ones defined by your [project's metadata](../metadata.md#dependencies). Entries support [context formatting](advanced.md#context-formatting).

```toml config-example
[tool.hatch.envs.test]
dependencies = [
  "coverage[toml]",
  "pytest",
  "pytest-cov",
  "pytest-mock",
]
```

If you define environments with dependencies that only slightly differ from their [inherited environments](#inheritance), you can use the `extra-dependencies` option to avoid redeclaring the `dependencies` option:

```toml config-example
[tool.hatch.envs.default]
dependencies = [
  "foo",
  "bar",
]

[tool.hatch.envs.experimental]
extra-dependencies = [
  "baz",
]
```

!!! tip
    Hatch uses [pip](https://github.com/pypa/pip) to install dependencies so any [configuration](https://pip.pypa.io/en/stable/topics/configuration/) it supports Hatch does as well. For example, if you wanted to only use a private repository you could set the `PIP_INDEX_URL` [environment variable](#environment-variables).

## Installation

### Features (extras) ### {: #features }

If your project defines [optional dependencies](../metadata.md#optional), you can select which groups to install using the `features` option:

```toml config-example
[tool.hatch.envs.nightly]
features = [
  "server",
  "grpc",
]
```

!!! note
    Features/optional dependencies are also known as `extras` in other tools.

### Dev mode

By default, environments will always reflect the current state of your project on disk. Set `dev-mode` to `false` to disable this behavior:

```toml config-example
[tool.hatch.envs.static]
dev-mode = false
```

### Skip install

By default, environments will install your project during creation. To ignore this step, set `skip-install` to `true`:

```toml config-example
[tool.hatch.envs.lint]
skip-install = true
```

## Environment variables

### Defined

You can define environment variables with the `env-vars` option:

```toml config-example
[tool.hatch.envs.docs]
dependencies = [
  "mkdocs"
]
[tool.hatch.envs.docs.env-vars]
SOURCE_DATE_EPOCH = "1580601600"
```

Values support [context formatting](advanced.md#context-formatting).

### Filters

By default, environments will have access to all environment variables. You can filter with wildcard patterns using the `env-include`/`env-exclude` options:

```toml config-example
[tool.hatch.envs.<ENV_NAME>]
env-include = [
  "FOO*",
]
env-exclude = [
  "BAR",
]
```

Exclusion patterns take precedence but will never affect [defined](#defined) environment variables.

## Scripts

You can define named scripts that may be [executed](../../environment.md#command-execution) or referenced at the beginning of other scripts. [Context formatting](advanced.md#context-formatting) is supported.

For example, in the following configuration:

```toml config-example
[tool.hatch.envs.test]
dependencies = [
  "coverage[toml]",
  "pytest",
  "pytest-cov",
  "pytest-mock",
]
[tool.hatch.envs.test.scripts]
run-coverage = "pytest --cov-config=pyproject.toml --cov=pkg --cov=tests"
run = "run-coverage --no-cov"
```

the `run` script would be expanded to:

```
pytest --cov-config=pyproject.toml --cov=pkg --cov=tests --no-cov
```

Scripts can also be defined as an array of strings.

```toml config-example
[tool.hatch.envs.style]
detached = true
dependencies = [
  "flake8",
  "black",
  "isort",
]
[tool.hatch.envs.style.scripts]
check = [
  "flake8 .",
  "black --check --diff .",
  "isort --check-only --diff .",
]
fmt = [
  "isort .",
  "black .",
  "check",
]
```

Similar to [make](https://www.gnu.org/software/make/manual/html_node/Errors.html), you can ignore the exit code of commands that start with `-` (a hyphen). For example, the script `error` defined by the following configuration would halt after the second command with `3` as the exit code:

```toml config-example
[tool.hatch.envs.test.scripts]
error = [
  "- exit 1",
  "exit 3",
  "exit 0",
]
```

### Extra scripts

Individual scripts [inherit](#inheritance) from parent environments just like options. To guarantee that individual scripts do not override those defined by parent environments, you can use the `extra-scripts` option instead which is only capable of adding scripts that have not been defined.

## Commands

All commands are able to use any defined [scripts](#scripts). Also like scripts, [context formatting](advanced.md#context-formatting) is supported and the exit code of commands that start with a hyphen will be ignored.

### Pre-install

You can run commands immediately before environments [install](#skip-install) your project.

```toml config-example
[tool.hatch.envs.<ENV_NAME>]
pre-install-commands = [
  "...",
]
```

### Post-install

You can run commands immediately after environments [install](#skip-install) your project.

```toml config-example
[tool.hatch.envs.<ENV_NAME>]
post-install-commands = [
  "...",
]
```

## Python version

The `python` option specifies which version of Python to use, or an absolute path to a Python interpreter:

```toml config-example
[tool.hatch.envs.<ENV_NAME>]
python = "3.10"
```

All [environment types](#type) should respect this option.

## Supported platforms

The `platforms` option indicates the operating systems with which the environment is compatible:

```toml config-example
[tool.hatch.envs.<ENV_NAME>]
platforms = ["linux", "windows", "macos"]
```

The following platforms are supported:

- `linux`
- `windows`
- `macos`

If unspecified, the environment is assumed to be compatible with all platforms.

## Description

The `description` option is purely informational and is displayed in the output of the [`env show`](../../cli/reference.md#hatch-env-show) command:

```toml config-example
[tool.hatch.envs.<ENV_NAME>]
description = """
Lorem ipsum ...
"""
```

## Type

An environment's `type` determines which [environment plugin](../../plugins/environment/reference.md) will be used for management. The only built-in environment type is [`virtual`](../../plugins/environment/virtual.md), which uses virtual Python environments.
