yatee

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Version: v0.6.0 Latest Latest
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Published: Oct 4, 2018 License: Apache-2.0 Imports: 6 Imported by: 0

README

What is yatee?

Yatee is a basic YAML templating engine whose input is a valid YAML file.

What does it support?

If, for, variable expansion, arithmetic expressions.

Show me some examples!

version: "3.4"
services:
  "@for i in 0..2":
    replica$i:
      image: superduperserver:latest
      command: /run $i
      port:
        - $(5000 + ($i*2))
        - $(5001 + ($i * 2))
  "@if ${myapp.debug}":
    debugger:
      image: debug
  "@if ! ${myapp.debug}":
    monitor:
      image: monitor
  "@for i in $myapp.services":
    "$i":
      image: $i:latest

When processed with the following settings file:

myapp:
  debug: false
  services:
    - nginx
    - redis

Will produce the following output:

services:
  monitor:
    image: monitor
  nginx:
    image: nginx:latest
  redis:
    image: redis:latest
  replica0:
    command: /run 0
    image: superduperserver:latest
    port:
    - "5000"
    - "5001"
  replica1:
    command: /run 1
    image: superduperserver:latest
    port:
    - "5002"
    - "5003"

How do I invoke it?

./yatee TEMPLATE_FILE SETTINGS_FILES...

How do I use it as a library?

The yatee go package exports the following two functions:

// LoadSettings loads a set of settings file and produce a property dictionary
func LoadSettings(files []string) (map[string]interface{}, error)
// Process resolves input templated yaml using values given in settings
func Process(inputString string, settings map[string]interface{}) (map[interface{}] interface{}, error)

Tell me more about the templating

All features at a glance

  • $foo.bar and ${foo.bar} are replaced by the value of foo.bar in the settings structure. Nesting is allowed.
  • ${foo?IF_TRUE:IF_FALSE} is replaced by IF_TRUE if foo in settings is true (not empty, 0 or false).
  • $(expr) is evaluated as an arithmetic expression. Integers, parenthesis, and the operators '+-*/%' are supported. Note that there is no operator precedence, evaluation is from left to right.
  • $$ is replaced by a single literal $ without any variable expansion.
  • A YAML key of @for VAR in begin..end or @for VAR in VALUE LIST will inject the value in the parent node for each value of VAR.
  • A YAML key of @if VALUE will inject its content in the parent node only if VAULE is not false (0, empty or 'false'). A prefix '!' is supported to negate the value. A @else dict can be specified under the @if node, and will be injected if the condition is false.
  • A YAML key of @switch VALUE will inject it's sub-key's value matching VALUE to the parent node, or inject the value under the default key if present and no match is found.
  • A YAML value of @if (EXPR) VALUE in a list will be replaced by VALUE if EXPR is true, suppressed otherwise

Variable expansion examples

All examples below use the following settings:

app:
  debug: true
  release: false
foo: bar
bar: baz
count: 2
Input Output
${app.debug} true
${foo}${bar} barbaz
${$foo} baz
$(1+2*3) 9
$(1+(2*3)) 7
$($count + 40) 42
${app.debug?foo:bar} foo
${app.release?foo:bar} bar
$$foo $$foo
$$$foo $$bar

Control flow examples

Using the same settings as above.

If
"@if !$app.release":
 shown: nope
 "@else":
   shown: yes
somelist:
  - a
  - @if ($app.debug) b
  - @if ($app.release) c
  - d

produces:

shown: yes
somelist:
- a
- b
- d
For
"@for v in 0..$(count)":
  key$v: val$($v + 1)
"@for v in a b c":
  key$v: val$v

produces:

key0: val1
key1: val2
keya: vala
keyb: valb
keyc: valc
Switch
"@switch $foo":
  baz:
    isbaz: 1
  bar:
    isbar: 1
  default:
    isother: 1
"@switch $bar":
  foo:
    isfoo: 2
  default:
    isother:2

produces

isbar: 1
isother: 2

Documentation

Index

Constants

View Source
const (
	// OptionErrOnMissingKey if set will make rendering fail if a non-existing variable is used
	OptionErrOnMissingKey = "ErrOnMissingKey"
)

Variables

This section is empty.

Functions

func LoadSettings

func LoadSettings(files []string) (map[string]interface{}, error)

LoadSettings loads a set of settings file and produce a property dictionary

func Process

func Process(inputString string, settings map[string]interface{}, opts ...string) (map[interface{}]interface{}, error)

Process resolves input templated yaml using values given in settings

func ProcessStrings

func ProcessStrings(input, settings string) (string, error)

ProcessStrings resolves input templated yaml using values in settings yaml

Types

This section is empty.

Source Files

Directories

Path Synopsis

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