protoc-gen-gotemplate/vendor/github.com/Masterminds/sprig/docs/defaults.md

Default Functions

Sprig provides tools for setting default values for templates.

default

To set a simple default value, use default:

default "foo" .Bar

In the above, if .Bar evaluates to a non-empty value, it will be used. But if it is empty, foo will be returned instead.

The definition of "empty" depends on type:

• Numeric: 0
• String: ""
• Lists: []
• Dicts: {}
• Boolean: false
• And always nil (aka null)

For structs, there is no definition of empty, so a struct will never return the default.

empty

The empty function returns true if the given value is considered empty, and false otherwise. The empty values are listed in the default section.

empty .Foo

Note that in Go template conditionals, emptiness is calculated for you. Thus, you rarely need if empty .Foo. Instead, just use if .Foo.

coalesce

The coalesce function takes a list of values and returns the first non-empty one.

coalesce 0 1 2

The above returns 1.

This function is useful for scanning through multiple variables or values:

coalesce .name .parent.name "Matt"

The above will first check to see if .name is empty. If it is not, it will return that value. If it is empty, coalesce will evaluate .parent.name for emptiness. Finally, if both .name and .parent.name are empty, it will return Matt.