handlebars_misc_helpers

A collection of helpers for handlebars (rust) to manage String, JSON, YAML, TOML, path, file, and HTTP requests.

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

To use a 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 the crate's features:

default = ["string", "http_attohttpc", "json", "jsonnet", "regex", "uuid"]
http_attohttpc = ["dep:attohttpc"]
http_reqwest = ["dep:reqwest"]
json = [
    "dep:jmespath",
    "dep:serde",
    "dep:serde_json",
    "dep:serde_yaml",
    "dep:toml",
]
jsonnet = ["dep:jsonnet-rs"]
jsontype = ["dep:serde_json"]
regex = ["dep:regex"]
string = ["dep:cruet", "dep:enquote", "jsontype"]
uuid = ["dep:uuid"]

• String transformation
• Regular expression
• UUID
• HTTP content
• Path extraction
• File
• Environment variable
• JSON & YAML & TOML
  • Helpers
  • Blocks
  • Edition via Jsonnet
• Assign, set
• Replace section

String transformation

Regular expression

UUID

HTTP content

The helpers can render the body's response from an HTTP request.

Path extraction

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

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

File

Helper to read file content.

Environment variable

The helper can get environment variables.

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

JSON & YAML & TOML

Helpers

• 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 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"

Blocks

{{#from_json format="toml"}}
{"foo": {"hello":"1.2.3", "bar":{"baz":true} } }
{{/from_json}}

[foo]
hello = "1.2.3"
[foo.bar]
baz = true

{{#to_json format="toml"}}
[foo]
bar = { baz = true }
hello = "1.2.3"
{{/to_json}}

{
  "foo": {
    "bar": {
      "baz": true
    },
    "hello": "1.2.3"
  }
}

{{#from_json format="yaml"}}
{"foo":{"bar":{"baz":true}}}
{{/from_json}}

foo:
  bar:
    baz: true

{{#to_json format="yaml"}}
foo:
    bar:
        baz: true
{{/to_json}}

{
  "foo": {
    "bar": {
      "baz": true
    }
  }
}

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

Edition via Jsonnet

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

{{#jsonnet}}
local v = {"foo":{"bar":{"baz":false}}};
v {
  "foo" +: {
      "bar" +: {
          "baz2": true
      }
  }
}
{{/jsonnet}}

{
  "foo": {
      "bar": {
          "baz": false,
          "baz2": true
      }
  }
}

Assign, set

The helpers can assign a variable to use later in the template.

⚠️ assign is deprecated and replaced by set (more compact and allows multiple assignments in one call)

Replace section

This helper can replace a section delimited by a boundary.

For example with this template:

{{~#replace_section  begin="<!-- #region head-->" end="<!-- #endregion head -->" content }}
This is the new content of the block
{{~/replace_section}}

The content having

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <!-- #region head-->
    Something by default
    <!-- #endregion head -->
  </body>
</html>

The content between <!-- #region head--> and <!-- #endregion head --> is replaced by the result of the inner template:

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <!-- #region head-->This is the new content of the block<!-- #endregion head -->
  </body>
</html>

Note: you can remove the boundary by adding remove_boundaries=true.