srcgen

srcgen

generate source code from data

Template

Uses standard go templates with the default delimiters set to <% %>, this can be changed on a per template basis.

Creating a Template

Templates is stored in the template folder, where a folder specify the template name.

Example: We have a template named 'readme' the folder structure should look like this.

./TemplatePath/readme/readme.md

By default srcgen will traverse all files in the folder and execute them as templates, how ever more complex behavior can be defined using a template settings file.

Template Settings

Template Functions

srcgen uses the Go html/template library for its template engine. It is an extremely lightweight engine that provides a very small amount of logic.

Go templates are lightweight but extensible. The following functions was added to the basic template logic.

(Go itself supplies built-in functions, including comparison operators and other basic tools; these are listed in the Go template documentation.)

General Template Functions

delimit

Loops through any array, slice or map and returns a string of all the values separated by the delimiter. There is an optional third parameter that lets you choose a different delimiter to go between the last two values. Maps will be sorted by the keys, and only a slice of the values will be returned, keeping a consistent output order.

Works on lists, taxonomies, terms, groups

e.g.

// Front matter
+++
tags: [ "tag1", "tag2", "tag3" ]
+++

// Used anywhere in a template
Tags: {{ delimit .Params.tags ", " }}

// Outputs Tags: tag1, tag2, tag3

// Example with the optional "last" parameter
Tags: {{ delimit .Params.tags ", " " and " }}

// Outputs Tags: tag1, tag2 and tag3

dict

Creates a dictionary (map[string, interface{}), expects parameters added in value:object fasion. Invalid combinations like keys that are not strings or uneven number of parameters, will result in an exception thrown Useful for passing maps to partials when adding to a template.

e.g. Pass into "foo.html" a map with the keys "important, content"

{{$important := .Site.Params.SomethingImportant }}
{{range .Site.Params.Bar}}
    {{partial "foo" (dict "content" . "important" $important)}}
{{end}}

"foo.html"

Important {{.important}}
{{.content}}

or Create a map on the fly to pass into

{{partial "foo" (dict "important" "Smiles" "content" "You should do more")}}

echoParam

Prints a parameter if it is set.

e.g. {{ echoParam .Params "project_url" }}

eq

Returns true if the parameters are equal.

e.g.

{{ if eq .Section "blog" }}current{{ end }}

first

Slices an array to only the first N elements.

Works on lists, taxonomies, terms, groups

e.g.

{{ range first 10 .Data.Pages }}
    {{ .Render "summary" }}
{{ end }}

last

Slices an array to only the last N elements.

Works on lists, taxonomies, terms, groups

e.g.

{{ range last 10 .Data.Pages }}
    {{ .Render "summary" }}
{{ end }}

after

Slices an array to only the items after the Nth item. Use this in combination with first to use both halves of an array split at item N.

Works on lists, taxonomies, terms, groups

e.g.

{{ range after 10 .Data.Pages }}
    {{ .Render "title" }}
{{ end }}

getenv

Returns the value of an environment variable.

Takes a string containing the name of the variable as input. Returns an empty string if the variable is not set, otherwise returns the value of the variable. Note that in Unix-like environments, the variable must also be exported in order to be seen by hugo.

e.g.

{{ getenv "HOME" }}

in

Checks if an element is in an array (or slice) and returns a boolean. The elements supported are strings, integers and floats (only float64 will match as expected). In addition, it can also check if a substring exists in a string.

e.g.

{{ if in .Params.tags "Git" }}Follow me on GitHub!{{ end }}

or

{{ if in "this string contains a substring" "substring" }}Substring found!{{ end }}

intersect

Given two arrays (or slices), this function will return the common elements in the arrays. The elements supported are strings, integers and floats (only float64).

A useful example of this functionality is a 'similar posts' block. Create a list of links to posts where any of the tags in the current post match any tags in other posts.

e.g.

<ul>
{{ $page_link := .Permalink }}
{{ $tags := .Params.tags }}
{{ range .Site.Pages }}
    {{ $page := . }}
    {{ $has_common_tags := intersect $tags .Params.tags | len | lt 0 }}
    {{ if and $has_common_tags (ne $page_link $page.Permalink) }}
        <li><a href="{{ $page.Permalink }}">{{ $page.Title }}</a></li>
    {{ end }}
{{ end }}
</ul>

isset

Returns true if the parameter is set. Takes either a slice, array or channel and an index or a map and a key as input.

e.g. {{ if isset .Params "project_url" }} {{ index .Params "project_url" }}{{ end }}

seq - not supported

Creates a sequence of integers. It's named and used as GNU's seq.

Some examples:

• 3 => 1, 2, 3
• 1 2 4 => 1, 3
• -3 => -1, -2, -3
• 1 4 => 1, 2, 3, 4
• 1 -2 => 1, 0, -1, -2

sort

Sorts maps, arrays and slices, returning a sorted slice. A sorted array of map values will be returned, with the keys eliminated. There are two optional arguments, which are sortByField and sortAsc. If left blank, sort will sort by keys (for maps) in ascending order.

Works on lists, taxonomies, terms, groups

e.g.

// Front matter
+++
tags: [ "tag3", "tag1", "tag2" ]
+++

// Site config
+++
[params.authors]
  [params.authors.Derek]
    "firstName"  = "Derek"
    "lastName"   = "Perkins"
  [params.authors.Joe]
    "firstName"  = "Joe"
    "lastName"   = "Bergevin"
  [params.authors.Tanner]
    "firstName"  = "Tanner"
    "lastName"   = "Linsley"
+++

// Use default sort options - sort by key / ascending
Tags: {{ range sort .Params.tags }}{{ . }} {{ end }}

// Outputs Tags: tag1 tag2 tag3

// Sort by value / descending
Tags: {{ range sort .Params.tags "value" "desc" }}{{ . }} {{ end }}

// Outputs Tags: tag3 tag2 tag1

// Use default sort options - sort by value / descending
Authors: {{ range sort .Site.Params.authors }}{{ .firstName }} {{ end }}

// Outputs Authors: Derek Joe Tanner

// Use default sort options - sort by value / descending
Authors: {{ range sort .Site.Params.authors "lastName" "desc" }}{{ .lastName }} {{ end }}

// Outputs Authors: Perkins Linsley Bergevin

where

Filters an array to only elements containing a matching value for a given field.

Works on lists, taxonomies, terms, groups

e.g.

{{ range where .Data.Pages "Section" "post" }}
   {{ .Content }}
{{ end }}

It can be used with dot chaining second argument to refer a nested element of a value.

e.g.

// Front matter on some pages
+++
series: golang
+++

{{ range where .Site.Pages "Params.series" "golang" }}
   {{ .Content }}
{{ end }}

It can also be used with an operator like !=, >=, in etc. Without an operator (like above), where compares a given field with a matching value in a way like = is specified.

e.g.

{{ range where .Data.Pages "Section" "!=" "post" }}
   {{ .Content }}
{{ end }}

Following operators are now available

• =, ==, eq: True if a given field value equals a matching value
• !=, <>, ne: True if a given field value doesn't equal a matching value
• >=, ge: True if a given field value is greater than or equal to a matching value
• >, gt: True if a given field value is greater than a matching value
• <=, le: True if a given field value is lesser than or equal to a matching value
• <, lt: True if a given field value is lesser than a matching value
• in: True if a given field value is included in a matching value. A matching value must be an array or a slice
• not in: True if a given field value isn't included in a matching value. A matching value must be an array or a slice

where and first can be stacked, e.g.:

{{ range first 5 (where .Data.Pages "Section" "post") }}
   {{ .Content }}
{{ end }}

Unset field

Filter only work for set fields. To check whether a field is set or exist, use operand nil.

This can be useful to filter a small amount of pages from a large pool. Instead of set field on all pages, you can set field on required pages only.

Only following operators are available for nil

• =, ==, eq: True if the given field is not set.
• !=, <>, ne: True if the given field is set.

e.g.

{{ range where .Data.Pages ".Params.specialpost" "!=" nil }}
   {{ .Content }}
{{ end }}

Math

Function	Description	Example
add	Adds two integers.	{{add 1 2}} → 3
div	Divides two integers.	{{div 6 3}} → 2
mod	Modulus of two integers.	{{mod 15 3}} → 0
modBool	Boolean of modulus of two integers. true if modulus is 0.	{{modBool 15 3}} → true
mul	Multiplies two integers.	{{mul 2 3}} → 6
sub	Subtracts two integers.	{{sub 3 2}} → 1

Strings

chomp

Removes any trailing newline characters. Useful in a pipeline to remove newlines added by other processing (including markdownify).

e.g., {{chomp "<p>Blockhead</p>\n"}} → "<p>Blockhead</p>"

lower

Converts all characters in string to lowercase.

e.g. {{lower "BatMan"}} → "batman"

pluralize

Pluralize the given word with a set of common English pluralization rules.

e.g. {{ "cat" | pluralize }} → "cats"

replace

Replaces all occurrences of the search string with the replacement string.

e.g. {{ replace "Batman and Robin" "Robin" "Catwoman" }} → "Batman and Catwoman"

singularize

Singularize the given word with a set of common English singularization rules.

e.g. {{ "cats" | singularize }} → "cat"

slicestr

Slicing in slicestr is done by specifying a half-open range with two indices, start and end. For example, 1 and 4 creates a slice including elements 1 through 3. The end index can be omitted; it defaults to the string's length.

e.g.

• {{slicestr "BatMan" 3}} → "Man"
• {{slicestr "BatMan" 0 3}} → "Bat"

substr

Extracts parts of a string, beginning at the character at the specified position, and returns the specified number of characters.

It normally takes two parameters: start and length. It can also take one parameter: start, i.e. length is omitted, in which case the substring starting from start until the end of the string will be returned.

To extract characters from the end of the string, use a negative start number.

In addition, borrowing from the extended behavior described at http://php.net/substr, if length is given and is negative, then that many characters will be omitted from the end of string.

e.g.

• {{substr "BatMan" 0 -3}} → "Bat"
• {{substr "BatMan" 3 3}} → "Man"

title

Converts all characters in string to titlecase.

e.g. {{title "BatMan"}} → "Batman"

trim

Returns a slice of the string with all leading and trailing characters contained in cutset removed.

e.g. {{ trim "++Batman--" "+-" }} → "Batman"

upper

Converts all characters in string to uppercase.

e.g. {{upper "BatMan"}} → "BATMAN"

Content Views

Render

Takes a view to render the content with. The view is an alternate layout, and should be a file name that points to a template in one of the locations specified in the documentation for Content Views.

This function is only available on a piece of content, and in list context.

This example could render a piece of content using the content view located at /layouts/_default/summary.html:

{{ range .Data.Pages }}
    {{ .Render "summary"}}
{{ end }}

Advanced

apply

Given a map, array, or slice, returns a new slice with a function applied over it. Expects at least three parameters, depending on the function being applied. The first parameter is the sequence to operate on; the second is the name of the function as a string, which must be in the Hugo function map (generally, it is these functions documented here). After that, the parameters to the applied function are provided, with the string "." standing in for each element of the sequence the function is to be applied against. An example is in order:

+++
names: [ "Derek Perkins", "Joe Bergevin", "Tanner Linsley" ]
+++

{{ apply .Params.names "urlize" "." }} → [ "derek-perkins", "joe-bergevin", "tanner-linsley" ]

This is roughly equivalent to:

{{ range .Params.names }}{{ . | urlize }}{{ end }}

However, it isn’t possible to provide the output of a range to the delimit function, so you need to apply it. A more complete example should explain this. Let's say you have two partials for displaying tag links in a post, "post/tag/list.html" and "post/tag/link.html", as shown below.

<!-- post/tag/list.html -->
{{ with .Params.tags }}
<div class="tags-list">
  Tags:
  {{ $len := len . }}
  {{ if eq $len 1 }}
    {{ partial "post/tag/link" (index . 0) }}
  {{ else }}
    {{ $last := sub $len 1 }}
    {{ range first $last . }}
      {{ partial "post/tag/link" . }},
    {{ end }}
    {{ partial "post/tag/link" (index . $last) }}
  {{ end }}
</div>
{{ end }}


<!-- post/tag/link.html -->
<a class="post-tag post-tag-{{ . | urlize }}" href="/tags/{{ . | urlize }}">{{ . }}</a>

This works, but the complexity of "post/tag/list.html" is fairly high; the Hugo template needs to perform special behaviour for the case where there’s only one tag, and it has to treat the last tag as special. Additionally, the tag list will be rendered something like "Tags: tag1 , tag2 , tag3" because of the way that the HTML is generated and it is interpreted by a browser.

This is Hugo. We have a better way. If this were your "post/tag/list.html" instead, all of those problems are fixed automatically (this first version separates all of the operations for ease of reading; the combined version will be shown after the explanation).

<!-- post/tag/list.html -->
{{ with.Params.tags }}
<div class="tags-list">
  Tags:
  {{ $sort := sort . }}
  {{ $links := apply $sort "partial" "post/tag/link" "." }}
  {{ $clean := apply $links "chomp" "." }}
  {{ delimit $clean ", " }}
</div>
{{ end }}

In this version, we are now sorting the tags, converting them to links with "post/tag/link.html", cleaning off stray newlines, and joining them together in a delimited list for presentation. That can also be written as:

<!-- post/tag/list.html -->
{{ with.Params.tags }}
<div class="tags-list">
  Tags:
  {{ delimit (apply (apply (sort .) "partial" "post/tag/link" ".") "chomp" ".") ", " }}
</div>
{{ end }}

apply does not work when receiving the sequence as an argument through a pipeline.

---

base64Encode and base64Decode

base64Encode and base64Decode let you easily decode content with a base64 encoding and vice versa through pipes. Let's take a look at an example:

{{ "Hello world" | base64Encode }}
<!-- will output "SGVsbG8gd29ybGQ=" and -->

{{ "SGVsbG8gd29ybGQ=" | base64Decode }}
<!-- becomes "Hello world" again. -->

You can also pass other datatypes as argument to the template function which tries to convert them. Now we use an integer instead of a string:

{{ 42 | base64Encode | base64Decode }}
<!-- will output "42". Both functions always return a string. -->

Tip: Using base64 to decode and encode becomes really powerful if we have to handle responses of APIs.

{{ $resp := getJSON "https://api.github.com/repos/spf13/hugo/readme"  }}
{{ $resp.content | base64Decode | markdownify }}

The response of the GitHub API contains the base64-encoded version of the README.md in the Hugo repository. Now we can decode it and parse the Markdown. The final output will look similar to the rendered version on GitHub.