# handlebars_misc_helpers <!-- omit in toc -->
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[](https://crates.io/crates/handlebars_misc_helpers)
[](https://docs.rs/handlebars_misc_helpers/)
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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:
```handlebars
// arguments are space separated
{{ helper_name arguments}}
```
To chain helpers, use parenthesis:
```handlebars
{{ 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](https://handlebarsjs.com/)
To not "import" useless dependencies, use crate's features:
```toml
[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](#string-transformation)
- [Http content](#http-content)
- [Path extraction](#path-extraction)
- [File](#file)
- [Environment variable](#environment-variable)
- [JSON & YAML & TOML](#json--yaml--toml)
- [Helpers](#helpers)
- [Blocks](#blocks)
- [Edition via jsonnet](#edition-via-jsonnet)
- [Assign](#assign)
## String transformation
| `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.
| `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 |
| parent | `"/hello/bar"` |
| extension | `"txt"` |
## File
Helper to read file content.
| `{{ 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 |
Specials environment variables are predefined (some of them come from [`std::env::consts` - Rust](https://doc.rust-lang.org/std/env/consts/index.html)):
<table>
<thead>
<tr>
<th>variable</th>
<th>possible values</th>
</tr>
</thead>
<tbody>
<tr><td><code>"ARCH"</code></td><td><ul>
<li>x86</li>
<li>x86_64</li>
<li>arm</li>
<li>aarch64</li>
<li>mips</li>
<li>mips64</li>
<li>powerpc</li>
<li>powerpc64</li>
<li>s390x</li>
<li>sparc64</li>
</ul></td></tr>
<tr><td><code>"DLL_EXTENSION"</code></td><td><ul>
<li>so</li>
<li>dylib</li>
<li>dll</li>
</ul></td></tr>
<tr><td><code>"DLL_PREFIX"</code></td><td><ul>
<li>lib</li>
<li>"" (an empty string)</li>
</ul></td></tr>
<tr><td><code>"DLL_SUFFIX"</code></td><td><ul>
<li>.so</li>
<li>.dylib</li>
<li>.dll</li>
</ul></td></tr>
<tr><td><code>"EXE_EXTENSION"</code></td><td><ul>
<li>exe</li>
<li>"" (an empty string)</li>
</ul></td></tr>
<tr><td><code>"EXE_SUFFIX"</code></td><td><ul>
<li>.exe</li>
<li>.nexe</li>
<li>.pexe</li>
<li>"" (an empty string)</li>
</ul></td></tr>
<tr><td><code>"FAMILY"</code></td><td><ul>
<li>unix</li>
<li>windows</li>
</ul></td></tr>
<tr><td><code>"OS"</code></td><td><ul>
<li>linux</li>
<li>macos</li>
<li>ios</li>
<li>freebsd</li>
<li>dragonfly</li>
<li>netbsd</li>
<li>openbsd</li>
<li>solaris</li>
<li>android</li>
<li>windows</li>
</ul></td></tr>
<tr>
<td><code>"USERNAME"</code></td>
<td>try to find the current username, in the order:<ol>
<li>environment variable <code>"USERNAME"</code></li>
<li>environment variable <code>"username"</code></li>
<li>environment variable <code>"USER"</code></li>
<li>environment variable <code>"user"</code></li>
</ol></td>
</tr>
</tbody>
</table>
## JSON & YAML & TOML
### Helpers
- `json_query query:String data:Json`: Helper able to extract information from json using [JMESPath](http://jmespath.org/) syntax for `query`.
- `json_str_query query:String data:String`: Helper able to extract information from json using [JMESPath](http://jmespath.org/) 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"`
| `{{ 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` |
### Blocks
<table>
<tr>
<td><pre><code>{{#from_json format="toml"}}
{"foo": {"hello":"1.2.3", "bar":{"baz":true} } }
{{/from_json}}
</code></pre>
</td>
<td><pre><code>[foo]
hello = "1.2.3"
[foo.bar]
baz = true</code></pre></td>
</tr>
<tr>
<td><pre><code>{{#to_json format="toml"}}
[foo]
bar = { baz = true }
hello = "1.2.3"
{{/to_json}}</code></pre>
</td>
<td><pre><code>{
"foo": {
"bar": {
"baz": true
},
"hello": "1.2.3"
}
}</code></pre></td>
</tr>
<tr>
<td><pre><code>{{#from_json format="toml"}}
{"foo":{"bar":{"baz":true}}}
{{/from_json}}</code></pre>
</td>
<td><pre><code>foo:
bar:
baz: true</code></pre></td>
</tr>
<tr>
<td><pre><code>{{#to_json format="yaml"}}
foo:
bar:
baz: true
{{/to_json}}</code></pre>
</td>
<td><pre><code>{
"foo": {
"bar": {
"baz": true
}
}
}</code></pre></td>
</tr>
</table>
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](https://jsonnet.org/learning/tutorial.html) 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.
<table>
<tr>
<td><pre><code>{{#jsonnet}}
local v = {"foo":{"bar":{"baz":false}}};
v {
"foo" +: {
"bar" +: {
"baz2": true
}
}
}
{{/jsonnet}}</code></pre>
</td>
<td><pre><code>{
"foo": {
"bar": {
"baz": false,
"baz2": true
}
}
}</code></pre></td>
</tr>
</table>
## Assign
Helper able to assign (to set) a variable to use later in the template.
| `{{ assign "foo" "{}" }}` | `` |
| `{{ assign "foo" "{}" }}{{ foo }}` | `{}` |
| `{{ assign "foo" "hello world" }}{{ foo }}` | `hello world` |
| `{{ assign "foo" {} }}{{ foo }}` | `[object]` |
| `{{ assign "foo" {"bar": 33} }}{{ foo }}` | `[object]` |