handlebars_misc_helpers 0.11.2

A collection of helpers for handlebars (rust) to manage string, json, yaml, toml, path, file, http request.
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Project Status: WIP – Initial development is in progress, but there has not yet been a stable, usable release suitable for the public. Actions Status test coverage

A collection of helpers for handlebars (rust) to manage string, json, yaml, toml, path, file, http request.

Helpers extend the template to generate or to transform content. Few helpers are included, but if you need more helpers, ask via an issue or a PR.

To use an helper:

// arguments are space separated
{{ helper_name arguments}}

To chain helpers, use parenthesis:

{{ to_upper_case (to_singular "Hello foo-bars") }}
// -> BAR

{{ first_non_empty (unquote (json_str_query "package.edition" (read_to_str "Cargo.toml") format="toml")) (env_var "MY_VERSION") "foo" }}
// -> 2018

see Handlebars templating language

To not "import" useless dependencies, use crate's features:

default = [ "string", "http", "json", "jsonnet" ]
string = [ "Inflector", "enquote" ]
http = [ "attohttpc" ]
json = [ "lazy_static", "serde", "serde_json", "serde-transcode", "serde_yaml", "toml" ]
jsonnet = [ "jsonnet-rs" ]

String transformation

helper signature usage sample sample out
replace s:String from:String to:String replace "Hello old" "old" "new" "Hello new"
to_lower_case s:String to_lower_case "Hello foo-bars" "hello foo-bars"
to_upper_case s:String to_upper_case "Hello foo-bars" "HELLO FOO-BARS"
to_camel_case s:String to_camel_case "Hello foo-bars" "helloFooBars"
to_pascal_case s:String to_pascal_case "Hello foo-bars" "HelloFooBars"
to_snake_case s:String to_snake_case "Hello foo-bars" "hello_foo_bars"
to_screaming_snake_case s:String to_screaming_snake_case "Hello foo-bars" "HELLO_FOO_BARS"
to_kebab_case s:String to_kebab_case "Hello foo-bars" "hello-foo-bars"
to_train_case s:String to_train_case "Hello foo-bars" "Hello-Foo-Bars"
to_sentence_case s:String to_sentence_case "Hello foo-bars" "Hello foo" bars
to_title_case s:String to_title_case "Hello foo-bars" "Hello Foo Bars"
to_class_case s:String to_class_case "Hello foo-bars" "HelloFooBar"
to_table_case s:String to_table_case "Hello foo-bars" "hello_foo_bars"
to_plural s:String to_plural "Hello foo-bars" "bars"
to_singular s:String to_singular "Hello foo-bars" "bar"
trim s:String trim " foo " "foo"
trim_start s:String trim_start " foo " "foo "
trim_end s:String trim_end " foo " " foo"
unquote s:String unquote "\"foo\"" "foo"
enquote symbol:String s:String enquote "" "foo" "\"foo\""
first_non_empty s:String+ first_non_empty "" null "foo" "bar" "foo"

Http content

Helper able to render body response from an http request.

helper signature usage sample
http_get url:String http_get "http://hello/..."
gitignore_io templates:String gitignore_io "rust,visualstudiocode"

Path extraction

Helper able to extract (or transform) path (defined as string).

for the same input: "/hello/bar/foo.txt"

helper_name sample output
file_name "foo.txt"
parent "/hello/bar"
extension "txt"


Helper to read file content.

usage output
{{ read_to_str "/foo/bar" }} content of file /foo/bar
{{ read_to_str "file/does/not/exist" }} empty string

Environment variable

Helper able to get environment variables.

helper_name usage
env_var env_var "HOME"

Specials environment variables are predefined (some of them come from std::env::consts - Rust):



  • json_query query:String data:Json: Helper able to extract information from json using JMESPath syntax for query.
  • json_str_query query:String data:String: Helper able to extract information from json using JMESPath syntax for query, data follows the requested format.
  • json_to_str data:Json: convert a json data into a string following the requested format.
  • str_to_json data:String: convert(parse) a string into a json following the requested format.

The optional requested format, is the format of the string with data:

  • "json" (default if omitted)
  • "json_pretty" json with indentation,...
  • "yaml"
  • "toml"
  • "toml_pretty"
usage output
{{ json_query "foo" {} }} ``
{{ json_to_str ( json_query "foo" {"foo":{"bar":{"baz":true}}} ) }} {"bar":{"baz":true}}
{{ json_to_str ( json_query "foo" (str_to_json "{\"foo\":{\"bar\":{\"baz\":true}}}" ) ) }} {"bar":{"baz":true}}
{{ json_str_query "foo" "{\"foo\":{\"bar\":{\"baz\":true}}}" }} {"bar":{"baz":true}}
{{ json_str_query "foo.bar.baz" "{\"foo\":{\"bar\":{\"baz\":true}}}" }} true
{{ json_str_query "foo" "foo:\n bar:\n baz: true\n" format="yaml"}} bar:\n baz: true\n
{{ json_to_str ( str_to_json "{\"foo\":{\"bar\":{\"baz\":true}}}" format="json") format="yaml"}} foo:\n bar:\n baz: true\n


[foo.bar] baz = true

Note: YAML & TOML content are used as input and output format for json data. So capabilities are limited to what json support (eg. no date-time type like in TOML).

Edition via jsonnet

For more advanced edition of json, you can use jsonnet.

A data templating language for app and tool developers

  • See the doc of jsonnet for more samples, syntax info,...
  • This block can be combined with conversion helper/block for YAML & TOML to provide edition capabilities for those format
  • the output should a valid json, except if string_output = false is set as parameter of the block.


Helper able to assign (to set) a variable to use later in the template.

usage output
{{ assign "foo" "{}" }} ``
{{ assign "foo" "{}" }}{{ foo }} {}
{{ assign "foo" "hello world" }}{{ foo }} hello world
{{ assign "foo" {} }}{{ foo }} [object]
{{ assign "foo" {"bar": 33} }}{{ foo }} [object]