lang-ref-ytt-library.md

ytt Library: Library module

Library module @ytt:library provides a way to programmatically get result of templates included in a library. Libraries are found within _ytt_lib subdirectory.

• load("@ytt:library", "library")

# build library instance
app1 = library.get("app")

# build new copy of library with data values (does not mutate app1)
app1_with_vals = app1.with_data_values({"name": "app1"})

# return results of all YAML templates
app1_with_vals.eval()

# return url function defined within app library
url_func = app1_with_vals.export("url")
url_func() # result of url function

• library.get(name) (name: string, returned: library): returns library object that is backed by content under _ytt_lib/<name> (found in the same directory as the file containing this call). name could contain '/' slashes for directories (e.g. github.com/k14s/k8s-lib/app).

• x.with_data_values(vals) (x: library, vals: dict or YAML fragment, returned: library): returns a new library copy with added data values. Given data values are overlayed on top of data values found within library.

#@ def app_vals():
name: app1
env_vars:
  #@overlay/match missing_ok=True
  custom_key: val
#@ end

#! with_data_values 
#@ app1_with_vals = app1.with_data_values(app_vals())

• x.eval() (x: library, returned: YAML document set): returns computed YAML document set based on library configuration and data values.

• x.export(name, [path=]) (x: library, name: string, path: string, returned: any value including function): returns value of a symbol found within a library. Typically used to export a function but could also be used for variables. path keyword argument can specify location for the symbol if name is not unique within a library (path should not be used unless there are multiple symbols with the same name).

url_func = app1_with_vals.export("url", path="config.lib.yml")

Examples

See ytt-library-module example.