handlebars_misc_helpers

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:

[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
• Http content
• Path extraction
• File
• Environment variable
• JSON & YAML & TOML
  • Helpers
  • Blocks
  • Edition via jsonnet
• Assign

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"

File

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):

variable	possible values
"ARCH"	x86 x86_64 arm aarch64 mips mips64 powerpc powerpc64 s390x sparc64
"DLL_EXTENSION"	so dylib dll
"DLL_PREFIX"	lib "" (an empty string)
"DLL_SUFFIX"	.so .dylib .dll
"EXE_EXTENSION"	exe "" (an empty string)
"EXE_SUFFIX"	.exe .nexe .pexe "" (an empty string)
"FAMILY"	unix windows
"OS"	linux macos ios freebsd dragonfly netbsd openbsd solaris android windows
"USERNAME"	try to find the current username, in the order: environment variable "USERNAME" environment variable "username" environment variable "USER" environment variable "user"

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 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

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="toml"}} {"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 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.

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

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

Assign

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]