Purl (purl v0.3.0)

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Elixir Implementation of the purl (package url) specification.

Specification

https://github.com/package-url/purl-spec

Format: pkg:type/namespace/name@version?qualifiers#subpath

License

A lot of the documentation was taken directly from the specification. It is licensed under the MIT License:

Copyright (c) the purl authors

Permission is hereby granted, free of charge, to any person obtaining a copy of
this software and associated documentation files (the "Software"), to deal in
the Software without restriction, including without limitation the rights to
use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
the Software, and to permit persons to whom the Software is furnished to do so,
subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Summary

Types

name()

the name of the package

namespace()

some name prefix such as a Maven groupid, a Docker image owner, a GitHub user or organization

namespace_segment()

Segment of the namespace

parse_error()
qualifier_key()

qualifier key

qualifier_value()

qualifier value

qualifiers()

extra qualifying data for a package such as an OS, architecture, a distro, etc.

subpath()

extra subpath within a package, relative to the package root

subpath_segment()

subpath segment

t()

Package URL struct

type()

the package "type" or package "protocol" such as maven, npm, nuget, gem, pypi, etc.

version()

the version of the package

Functions

from_resource_uri(uri, fallback_version \\ nil)

Convert known URLs to purl

new(purl)

Creates a new purl struct from a Purl, URI or string.

new!(purl)

Similar to new/1 but raises URI.Error, Purl.Error.InvalidField or Purl.Error.InvalidURI if an invalid input is given.

to_string(purl)

Formats purl as string

to_uri(purl)

Converts a purl to a URI

Types

name()

@type name() :: :purl.name()

the name of the package

namespace()

@type namespace() :: :purl.namespace()

some name prefix such as a Maven groupid, a Docker image owner, a GitHub user or organization

The values are type-specific.

namespace_segment()

@type namespace_segment() :: :purl.namespace_segment()

Segment of the namespace

Validation

  • must not contain a '/'
  • must not be empty
  • A URL host or Authority must NOT be used as a namespace. Use instead a repository_url qualifier. Note however that for some types, the namespace may look like a host.

parse_error()

@type parse_error() ::
  %URI.Error{__exception__: true, action: term(), part: term(), reason: term()}
  | Purl.Error.InvalidField.t()
  | Purl.Error.DuplicateQualifier.t()
  | Purl.Error.InvalidScheme.t()
  | Purl.Error.SpecialCaseFailed.t()

qualifier_key()

@type qualifier_key() :: :purl.qualifier_key()

qualifier key

Validation

  • The key must be composed only of ASCII letters and numbers, '.', '-' and '_' (period, dash and underscore)
  • A key cannot start with a number
  • A key must NOT be percent-encoded
  • A key is case insensitive. The canonical form is lowercase
  • A key cannot contains spaces

qualifier_value()

@type qualifier_value() :: :purl.qualifier_value()

qualifier value

Validation

  • value cannot be an empty string: a key=value pair with an empty value is the same as no key/value at all for this key

qualifiers()

@type qualifiers() :: :purl.qualifiers()

extra qualifying data for a package such as an OS, architecture, a distro, etc.

The values are type-specific.

Validation

  • key must be unique within the keys of the qualifiers string

subpath()

@type subpath() :: :purl.subpath()

extra subpath within a package, relative to the package root

subpath_segment()

@type subpath_segment() :: :purl.subpath_segment()

subpath segment

Validation

  • must not contain a '/'
  • must not be any of '..' or '.'
  • must not be empty

t()

@type t() :: %Purl{
  name: name(),
  namespace: namespace(),
  qualifiers: qualifiers(),
  subpath: subpath(),
  type: type(),
  version: version() | nil
}

Package URL struct

type()

@type type() :: :purl.type()

the package "type" or package "protocol" such as maven, npm, nuget, gem, pypi, etc.

Known types: https://github.com/package-url/purl-spec/blob/master/PURL-TYPES.rst

Validation

  • The package type is composed only of ASCII letters and numbers, '.', '+' and '-' (period, plus, and dash)
  • The type cannot start with a number
  • The type cannot contains spaces
  • The type must NOT be percent-encoded
  • The type is case insensitive. The canonical form is lowercase

version()

@type version() :: :purl.version() | Version.t()

the version of the package

A version is a plain and opaque string. Some package types use versioning conventions such as semver for NPMs or nevra conventions for RPMS. A type may define a procedure to compare and sort versions, but there is no reliable and uniform way to do such comparison consistently.

Functions

from_resource_uri(uri, fallback_version \\ nil)

@spec from_resource_uri(
  uri :: String.t() | URI.t(),
  fallback_version :: Version.t() | String.t() | nil
) ::
  {:ok, t()} | :error

Convert known URLs to purl

Currently Supported

  • GitHub: Repository HTTP / Git URL, Project URL
  • BitBucket: Repository HTTTP / Git URL, Project URL
  • Hex.pm package URL

new(purl)

@spec new(purl :: String.t() | URI.t() | t()) :: {:ok, t()} | {:error, parse_error()}

Creates a new purl struct from a Purl, URI or string.

Examples 

iex> Purl.new("pkg:hex/purl")
{:ok, %Purl{type: "hex", name: "purl"}}

new!(purl)

@spec new!(purl :: String.t() | URI.t() | t()) :: t()

Similar to new/1 but raises URI.Error, Purl.Error.InvalidField or Purl.Error.InvalidURI if an invalid input is given.

Examples 

iex> Purl.new!("pkg:hex/purl")
%Purl{type: "hex", name: "purl"}

iex> Purl.new!(">pkg:hex/purl")
** (URI.Error) cannot parse due to reason invalid_uri: ">"

iex> Purl.new!("pkg:hex*/purl")
** (Purl.Error.InvalidField) invalid field type, "hex*" given

to_string(purl)

@spec to_string(purl :: t()) :: String.t()

Formats purl as string

Examples 

iex> Purl.to_string(%Purl{type: "hex", name: "purl"})
"pkg:hex/purl"

to_uri(purl)

@spec to_uri(purl :: t()) :: URI.t()

Converts a purl to a URI

Examples 

iex> Purl.to_uri(%Purl{type: "hex", name: "purl"})
%URI{scheme: "pkg", path: "hex/purl"}