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package_metadata.md

File metadata and controls

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Package metadata

The metadata can be expressed in many media types: in the package tarball, it is as an "Erlang term file" that can be read with file:consult/1. This specification describes the format used in the package tarball.

Types

All types listed here are Erlang terms.

  • string - A UTF-8 encoded Erlang binary
  • boolean - A boolean (true or false)
  • list(Inner) - A list with an Inner type
  • kvlist(Key => Value) - A list with two element tuples where the first element is of type Key and the second Value

kvlists are normally generic in the sense that they can have any values for keys, but they can also allow only specific keys: kvlist(...) where the keys will be listed in relation to the type.

Format

All keys are strings.

  • name (string) (required)

    Package name

  • elixir (string) (optional)

    Version requirement on Elixir

  • version (string) (required)

    Release version, required to be in the Semantic Version format

  • app (string) (required)

    OTP application name, usually the same name as the package but can differ

  • description (string) (required)

    Package description, recommended to be a single paragraph

  • files (list(string)) (required)

    Files in the package tarball contents

  • licenses (list(string)) (required)

    The package's licenses

  • maintainers (list(string)) (optional)

    This field is deprecated!

    The package's maintainers, can be a list of names and/or emails

  • links (kvlist(string => string)) (optional)

    Links related to the package where the key is the link name and the value is the URL

  • requirements (kvlist(string => kvlist(...))) (required)

    All dependencies of the package where the key is the dependent name.

    • app (string) (required)

      OTP application name, usually the same name as the package

    • optional (boolean) (required)

      If the package is required or not

    • requirement (string) (required)

      Version requirement on the dependent

    • repository (string) (optional)

      Dependency repository

  • build_tools (list(string)) (required)

    Names of build tools that can build the package

  • extra (kvlist(string => kvlist(...))) (optional)

    Extra information about the package

Optional dependencies

An optional dependency will only be used if a package higher up the dependency chain also depends on it (only if that the dependency is not defined as optional as well).

Example

The ecto package has an optional dependency on postgrex. If a project X depends on ecto and postgrex, both dependencies will be used and ecto's version requirement on postgrex has to be satisfied. But if project X only depends on ecto without listing postgrex as a dependency, the package can be ignored.