transform.Unmarshal

Parses serialized data and returns a map or an array. Supports CSV, JSON, TOML, YAML, and XML.

Syntax

transform.Unmarshal [OPTIONS] INPUT

Returns

any

Alias

unmarshal

The input can be a string or a resource.

Unmarshal a string

{{ $string := `
title: Les Misérables
author: Victor Hugo
`}}

{{ $book := unmarshal $string }}
{{ $book.title }} → Les Misérables
{{ $book.author }} → Victor Hugo

Unmarshal a resource

Use the transform.Unmarshal function with global, page, and remote resources.

Global resource

A global resource is a file within the assets directory, or within any directory mounted to the assets directory.

assets/
└── data/
    └── books.json

{{ $data := dict }}
{{ $path := "data/books.json" }}
{{ with resources.Get $path }}
  {{ with . | transform.Unmarshal }}
    {{ $data = . }}
  {{ end }}
{{ else }}
  {{ errorf "Unable to get global resource %q" $path }}
{{ end }}

{{ range where $data "author" "Victor Hugo" }}
  {{ .title }} → Les Misérables
{{ end }}

Page resource

A page resource is a file within a page bundle.

content/
├── post/
│   └── book-reviews/
│       ├── books.json
│       └── index.md
└── _index.md

{{ $data := dict }}
{{ $path := "books.json" }}
{{ with .Resources.Get $path }}
  {{ with . | transform.Unmarshal }}
    {{ $data = . }}
  {{ end }}
{{ else }}
  {{ errorf "Unable to get page resource %q" $path }}
{{ end }}

{{ range where $data "author" "Victor Hugo" }}
  {{ .title }} → Les Misérables
{{ end }}

Remote resource

A remote resource is a file on a remote server, accessible via HTTP or HTTPS.

{{ $data := dict }}
{{ $url := "https://example.org/books.json" }}
{{ with try (resources.GetRemote $url) }}
  {{ with .Err }}
    {{ errorf "%s" . }}
  {{ else with .Value }}
    {{ $data = . | transform.Unmarshal }}
  {{ else }}
    {{ errorf "Unable to get remote resource %q" $url }}
  {{ end }}
{{ end }}

{{ range where $data "author" "Victor Hugo" }}
  {{ .title }} → Les Misérables
{{ end }}

When retrieving remote data, a misconfigured server may send a response header with an incorrect Content-Type. For example, the server may set the Content-Type header to application/octet-stream instead of application/json.

In these cases, pass the resource Content through the transform.Unmarshal function instead of passing the resource itself. For example, in the above, do this instead:

{{ $data = .Content | transform.Unmarshal }}

Working with CSV

Options

When unmarshaling a CSV file, provide an optional map of options.

delimiter: (string) The delimiter used. Default is ,.
comment: (string) The comment character used in the CSV. If set, lines beginning with the comment character without preceding whitespace are ignored.
lazyQuotes: New in v0.122.0; (bool) Whether to allow a quote in an unquoted field, or to allow a non-doubled quote in a quoted field. Default is false.
targetType: New in v0.146.7; (string) The target data type, either slice or map. Default is slice.

Examples

The examples below use this CSV file:

"name","type","breed","age"
"Spot","dog","Collie",3
"Rover","dog","Boxer",5
"Felix","cat","Calico",7

To render an HTML table from a CSV file:

{{ $data := slice }}
{{ $file := "pets.csv" }}
{{ with or (.Resources.Get $file) (resources.Get $file) }}
  {{ $opts := dict "targetType" "slice" }}
  {{ $data = transform.Unmarshal $opts . }}
{{ end }}

{{ with $data }}
  <table>
    <thead>
      <tr>
        {{ range index . 0 }}
          <th>{{ . }}</th>
        {{ end }}
      </tr>
    </thead>
    <tbody>
      {{ range . | after 1 }}
        <tr>
          {{ range . }}
            <td>{{ . }}</td>
          {{ end }}
        </tr>
      {{ end }}
    </tbody>
  </table>
{{ end }}

To extract a subset of the data, or to sort the data, unmarshal to a map instead of a slice:

{{ $data := slice }}
{{ $file := "pets.csv" }}
{{ with or (.Resources.Get $file) (resources.Get $file) }}
  {{ $opts := dict "targetType" "map" }}
  {{ $data = transform.Unmarshal $opts . }}
{{ end }}

{{ with sort (where $data "type" "dog") "name" "asc" }}
  <table>
    <thead>
      <tr>
        <th>name</th>
        <th>type</th>
        <th>breed</th>
        <th>age</th>
      </tr>
    </thead>
    <tbody>
      {{ range . }}
        <tr>
          <td>{{ .name }}</td>
          <td>{{ .type }}</td>
          <td>{{ .breed }}</td>
          <td>{{ .age }}</td>
        </tr>
      {{ end }}
    </tbody>
  </table>
{{ end }}

Working with XML

When unmarshaling an XML file, do not include the root node when accessing data. For example, after unmarshaling the RSS feed below, access the feed title with $data.channel.title.

<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom">
  <channel>
    <title>Books on Example Site</title>
    <link>https://example.org/books/</link>
    <description>Recent content in Books on Example Site</description>
    <language>en-US</language>
    <atom:link href="https://example.org/books/index.xml" rel="self" type="application/rss+xml" />
    <item>
      <title>The Hunchback of Notre Dame</title>
      <description>Written by Victor Hugo</description>
      <link>https://example.org/books/the-hunchback-of-notre-dame/</link>
      <pubDate>Mon, 09 Oct 2023 09:27:12 -0700</pubDate>
      <guid>https://example.org/books/the-hunchback-of-notre-dame/</guid>
    </item>
    <item>
      <title>Les Misérables</title>
      <description>Written by Victor Hugo</description>
      <link>https://example.org/books/les-miserables/</link>
      <pubDate>Mon, 09 Oct 2023 09:27:11 -0700</pubDate>
      <guid>https://example.org/books/les-miserables/</guid>
    </item>
  </channel>
</rss>

Get the remote data:

{{ $data := dict }}
{{ $url := "https://example.org/books/index.xml" }}
{{ with try (resources.GetRemote $url) }}
  {{ with .Err }}
    {{ errorf "%s" . }}
  {{ else with .Value }}
    {{ $data = . | transform.Unmarshal }}
  {{ else }}
    {{ errorf "Unable to get remote resource %q" $url }}
  {{ end }}
{{ end }}

Inspect the data structure:

<pre>{{ debug.Dump $data }}</pre>

List the book titles:

{{ with $data.channel.item }}
  <ul>
    {{ range . }}
      <li>{{ .title }}</li>
    {{ end }}
  </ul>
{{ end }}

Hugo renders this to:

<ul>
  <li>The Hunchback of Notre Dame</li>
  <li>Les Misérables</li>
</ul>

XML attributes and namespaces

Let’s add a lang attribute to the title nodes of our RSS feed, and a namespaced node for the ISBN number:

<?xml version="1.0" encoding="utf-8" standalone="yes"?>
<rss version="2.0"
  xmlns:atom="http://www.w3.org/2005/Atom"
  xmlns:isbn="http://schemas.isbn.org/ns/1999/basic.dtd"
>
  <channel>
    <title>Books on Example Site</title>
    <link>https://example.org/books/</link>
    <description>Recent content in Books on Example Site</description>
    <language>en-US</language>
    <atom:link href="https://example.org/books/index.xml" rel="self" type="application/rss+xml" />
    <item>
      <title lang="en">The Hunchback of Notre Dame</title>
      <description>Written by Victor Hugo</description>
      <isbn:number>9780140443530</isbn:number>
      <link>https://example.org/books/the-hunchback-of-notre-dame/</link>
      <pubDate>Mon, 09 Oct 2023 09:27:12 -0700</pubDate>
      <guid>https://example.org/books/the-hunchback-of-notre-dame/</guid>
    </item>
    <item>
      <title lang="fr">Les Misérables</title>
      <description>Written by Victor Hugo</description>
      <isbn:number>9780451419439</isbn:number>
      <link>https://example.org/books/les-miserables/</link>
      <pubDate>Mon, 09 Oct 2023 09:27:11 -0700</pubDate>
      <guid>https://example.org/books/les-miserables/</guid>
    </item>
  </channel>
</rss>

After retrieving the remote data, inspect the data structure:

<pre>{{ debug.Dump $data }}</pre>

Each item node looks like this:

{
  "description": "Written by Victor Hugo",
  "guid": "https://example.org/books/the-hunchback-of-notre-dame/",
  "link": "https://example.org/books/the-hunchback-of-notre-dame/",
  "number": "9780140443530",
  "pubDate": "Mon, 09 Oct 2023 09:27:12 -0700",
  "title": {
    "#text": "The Hunchback of Notre Dame",
    "-lang": "en"
  }
}

The title keys do not begin with an underscore or a letter—they are not valid identifiers. Use the index function to access the values:

{{ with $data.channel.item }}
  <ul>
    {{ range . }}
      {{ $title := index .title "#text" }}
      {{ $lang := index .title "-lang" }}
      {{ $ISBN := .number }}
      <li>{{ $title }} ({{ $lang }}) {{ $ISBN }}</li>
    {{ end }}
  </ul>
{{ end }}

Hugo renders this to:

<ul>
  <li>The Hunchback of Notre Dame (en) 9780140443530</li>
  <li>Les Misérables (fr) 9780451419439</li>
</ul>

Last updated: April 22, 2025 : content: Updates for v0.146.7 (5c2aa88b4)

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