Text Templating

Overview ¶

ytt supports text templating within YAML strings and .txt files.

Text templating is controlled via (@ and @) directives. These directives can be combined with following markers:

• = to output result; result must be of type string
• - to trim space either to the left (if next to opening directive) or right (if next to closing directive)

Examples:

• before (@ 123 @) middle (@= "tpl" @) after produces before middle tpl after
• before (@- 123 -@) middle (@-= "tpl" -@) after produces beforemiddletplafter

Inside YAML strings ¶

+ operand or string·format(...) method provide a good way to build strings:

• name: #@ name_prefix + "-secret"
• name: #@ name_prefix + "-" + str(1234)
• name: #@ "{}-secret-{}".format(name_prefix, name_suffix)

However, occasionally it might be useful to use text templating directly in YAML strings. To do so YAML node must be annotated with @yaml/text-templated-strings (v0.17.0+). Annotation will apply to node and its child nodes.

Examples:

• basic use

#@ val1 = "val1"
#@ val2 = "val2"

#@yaml/text-templated-strings
templated: "before (@= val1 @) middle (@= val2 @) after"

non_templated: "(@ something"

• nested nodes

#@ val1 = "val1"
#@ val2 = "val2"

#@yaml/text-templated-strings
---
key:
  nested_key_(@= val1 @): "middle (@= val2 @) after"

See Text template example in online playground.