XM

Beautiful Elixir DSL for building XML documents, backed by Saxy for escaping and encoding.

import XM

document do
  urlset xmlns: "http://www.sitemaps.org/schemas/sitemap/0.9" do
    for page <- pages do
      url do
        loc site_url <> page.path
        lastmod page.date
      end
    end
  end
end

XM is intentionally tiny: local calls become XML elements, keyword arguments become attributes, and normal Elixir expressions still work.

Features

Nested XML elements with Elixir do/end syntax.
Attributes via keyword lists or maps.
Dynamic/namespaced tag names with tag/2 and qname/2.
Namespace declarations with xmlns/1, xmlns/2, and declarative schema do ... end metadata.
Dotted namespace calls such as image.image do ... end for declared prefixes.
Optional XSD validation through XM.validate!/2 or compile-time global config.
Idiomatic %XM.Error{} exceptions for invalid documents, names, attributes, text, or schema validation.
for, if, unless, and case inside XML blocks.
Explicit text/1, comment/1, and cdata/1 nodes.
Binary rendering with render/2 and iodata rendering with render_iodata/2.
Iodata-first pipelines with tree do ... end |> render_iodata().
Saxy-backed escaping and XML encoding.

Installation

def deps do
  [
    {:xm, "~> 0.1.0"}
  ]
end

Examples

Sitemap

import XM

pages = [
  %{path: "/", date: ~D[2026-06-25]},
  %{path: "/about/", date: ~D[2026-06-25]}
]

xml =
  document do
    urlset xmlns: "http://www.sitemaps.org/schemas/sitemap/0.9" do
      for page <- pages do
        url do
          loc "https://example.com" <> page.path
          lastmod page.date
        end
      end
    end
  end

Atom entry with CDATA

import XM

document do
  entry do
    title "Hello"

    content type: "html" do
      cdata "<p>Hello from XML</p>"
    end
  end
end

Namespaces and schema declarations

schema do ... end is document metadata, not an XML element. XM injects namespace declarations into the document root and renders XSD locations as xsi:schemaLocation.

import XM

xml =
  document do
    schema do
      default "http://www.sitemaps.org/schemas/sitemap/0.9",
        location: "priv/schemas/sitemap.xsd"

      ns :image, "http://www.google.com/schemas/sitemap-image/1.1",
        location: "priv/schemas/sitemap-image.xsd"
    end

    urlset do
      url do
        loc "https://example.com/"

        image.image do
          image.loc "https://example.com/image.jpg"
        end
      end
    end
  end

Namespaced or dynamic tags

import XM

tree do
  tag qname(:media, :thumbnail), [xmlns(:media, "https://example.com/media"), url: "https://example.com/image.png"]
end

Iodata rendering

document do ... end is the convenience API for producing a binary XML document. For iodata, build nodes with tree do ... end and render explicitly:

import XM

iodata =
  tree do
    feed do
      title "Hello"
    end
  end
  |> XM.render_iodata()

IO.iodata_to_binary(iodata)

This mirrors common Elixir conventions: keep binary and iodata rendering as separate functions instead of overloading a single render/2 option.

XSD validation

Use XM.validate!/2 explicitly:

XM.validate!(xml)
XM.validate!(xml, schema: "priv/schemas/sitemap.xsd")
XM.validate!(xml, schemas: ["priv/schemas/sitemap.xsd", "priv/schemas/sitemap-image.xsd"])

Without explicit :schema/:schemas, XM reads schema locations from the parsed root element's xsi:schemaLocation or xsi:noNamespaceSchemaLocation attributes.

To validate every document do ... end, enable XM's global compile-time configuration before modules using document/2 are compiled:

config :xm, validate: true

The option is captured when the document do ... end macro expands. It is intentionally global; there is no per-document validate: option. If validation is enabled and the document does not declare schema locations, XM raises %XM.Error{reason: :missing_schema}.

XM