yglu 0.10.0

YAML glue for structural templating and processing

Yglu ᕄ

Yglu is YAML enriched with an advanced expression language. Unlike usual text templating, Yglu relies on the YAML structure and leverages its typing features combined with the YAQL query language.

This association enables templating and functional processing a bit like if YAML nodes where spreadsheet cells.

Yglu input documents are pure YAML using tags for computed nodes.

input a: 1 b: !? .a + 1

output a: 1 b: 2

input tags: !- - 'nginx:1.16' - 'node:13.6' - 'couchbase:9.3' image: !() !? $.split(':')[0]: version: !? $.split(':')[1] images: !? $_.tags .select(($_.image)($)) .aggregate($1.mergeWith($2), {})

output images: nginx: version: '1.16' node: version: '13.6' couchbase: version: '9.3'

In the example above, the tags sequence is hidden, image is a function (like a template block) and images is an expression which iterates through all tags, apply the image function to them and aggregate the individual results by merging them together as a mapping.

See the test samples for more examples.

Install

pip install yglu

Run

Usage: yglu [options] [<filename>]

Options:
  -v - -version          Print version and exit.
  -h - -help             Print help and exit.

Tags

Tags specify an alteration of the document structure.

Tag	Description
!?	Evaluate an expression. The result can be a scalar, mapping or sequence. Can also be used in mapping keys.
!-	Hide the node in the output but keep it accessible from expressions. When used with a scalar, it evaluates it as an expression.
!()	Make the node reusable in expressions as a function. It is also hidden.
!if	Shortcut for conditional merge of mappings. See merge.yml.

Expressions

Expressions are written in YAQL.

They are evaluated in a context with the following predefined variables:

Variable	Description
$_	Refers to the current document root. Can be omitted at the beginning of the expression if it starts with a dot.
$	Implicit argument of functions.
$env	Gives access to environment variables. Disabled by default. Set the $YGLU_ENABLE_ENV environment variable to enable.

Built-in Functions

In addition to standard YAQL operators, Yglu defines the following functions:

Function	Description
$import(filename)	Imports another document in the current node.

Planned Features

• Tag for merging mappings easily (e.g. conditionally)