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Butler Template Syntax

We use the template engine from Go. Here you can find an overview about all template features. We use a unique delimiter to avoid collsion with existing template engines.

Delimiter

Inside files you have to use:

butler{<expr>}

For directory or file names you have to use a different delimiter to save character because windows has a path limit. We recommend to use short question names in the survey-butler.yml.

{<expr>}

Where can I use templates?

  • Filenames
  • Directories
  • Template variables
  • Text files (.html, .md, .txt, .cshtml, .cs, .js ...)

Butler maintain a list of extensions of binary files and disallow the parsing of these files

Built in

Project details

  • butler{ .Project.Name } Return the project name
  • butler{ .Project.Description } Return the project description
  • butler{ .Date } Return the date (RFC3339)
  • butler{ .Year } Return the year (4-digits)

Trim spaces around template actions

{{23 -}} // remove trailing space
   <
{{- 45}} // remove leading space

formats as 23<45

Helper functions

String

  • butler{ toCamelCase $string } Convert argument to camelCase style string If argument is empty, return itself.
  • butler{ toPascalCase $string } Convert argument to PascalCase style string If argument is empty, return itself.
  • butler{ toSnakeCase $string } Convert argument to snake_case style string. If argument is empty, return itself.
  • butler{ toLowerCase $string } Convert argument to lowercase style string If argument is empty, return itself.
  • butler{ toUpperCase $string } Convert argument to UPPERCASE style string If argument is empty, return itself.
  • butler{ join $array $seperator } Join concatenates the elements of a to create a single string.
  • butler{ replace $old $new $limit } Replace returns a copy of the string s with the first n non-overlapping instances of old replaced by new.
  • butler{ contains $string $substring } Contains reports whether substr is within s.
  • butler{ index $string $substring } Contains reports whether substr is within s.
  • butler{ repeat $string $count } Repeat returns a new string consisting of count copies of the string s.
  • butler{ split $string $sep } Split slices s into all substrings separated by sep and returns a slice of the substrings between those separators.

Path

  • butler{ joinPath $path, $path2 } Joins any number of path elements into a single path, adding a Separator if necessary.
  • butler{ relPath $path } Returns a relative path that is lexically equivalent to targpath when joined to basepath with an intervening separator.
  • butler{ absPath $path } Returns an absolute representation of path.
  • butler{ basePath $path } Returns the last element of path.
  • butler{ extPath $path } Returns the file name extension used by path.

Regex

  • butler{ (regex "[0-9]+").FindString "I'm 26 years old" } Returns 26
  • For more methods look in the official Regex documentation

Generators

  • butler{ uuid } Returns a random UUID Version 4 string.
  • butler{ randomInt $min $max } Returns a random int between min and max

Environment

  • butler{ cwd } Returns the absolute path of the working directory.
  • butler{ env "name" } Returns the value of the environment variable.

All functions are written in camelCase

Define variables in templates

butler{$id := uuid} // generate id
butler{$id} // print id

Access to custom variables

Custom variables can be defined in the local butler.yml file or in the template butler-survey.yml file.

butler{ .Vars.company }

Interpolate custom variables

You have access to the survey result as well as template helper to define variables. This is useful if you want to work with short names in file or directory names.

variables:
  email: [email protected]
  projectName: "{ toUpperCase .Project.Name }"
  dbName: "{ toPascalCase getDb }"
  emailLowerCase: "{ toLowerCase .Vars.email }"

Inside your template

butler{ .Vars.projectName }

Get survey results

We generate getter functions to provide an easier access to survey results. If you have a question with the name color the result is accessible by:

butler{ getColor }

Get survey question

You can access the survey questions with the same approach

butler{ getColorQuestion }

Conditions in templates

butler{if eq getDb "mongodb"}
// your template
butler{end}

Conditional directories and files

Based on the survey you can decide which directories or files should be included or removed. The following example will include the folder when the question about the database will be answered with mongodb.

Folder: {if eq getDb `mongodb` }mongodb{end}

Build the filename based on an answer:

Filename: {print getColor `.md`}