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.

all

The all function takes a list of values and returns true if all values are non-empty.

all 0 1 2

The above returns false.

This function is useful for evaluating multiple conditions of variables or values:

all (eq .Request.TLS.Version 0x0304) (.Request.ProtoAtLeast 2 0) (eq .Request.Method "POST")

The above will check http.Request is POST with tls 1.3 and http/2.

any

The any function takes a list of values and returns true if any value is non-empty.

any 0 1 2

The above returns true.

This function is useful for evaluating multiple conditions of variables or values:

any (eq .Request.Method "GET") (eq .Request.Method "POST") (eq .Request.Method "OPTIONS")

The above will check http.Request method is one of GET/POST/OPTIONS.

fromJson, mustFromJson

fromJson decodes a JSON document into a structure. If the input cannot be decoded as JSON the function will return an empty string. mustFromJson will return an error in case the JSON is invalid.

fromJson "{\"foo\": 55}"

toJson, mustToJson

The toJson function encodes an item into a JSON string. If the item cannot be converted to JSON the function will return an empty string. mustToJson will return an error in case the item cannot be encoded in JSON.

toJson .Item

The above returns JSON string representation of .Item.

toPrettyJson, mustToPrettyJson

The toPrettyJson function encodes an item into a pretty (indented) JSON string.

toPrettyJson .Item

The above returns indented JSON string representation of .Item.

toRawJson, mustToRawJson

The toRawJson function encodes an item into JSON string with HTML characters unescaped.

toRawJson .Item

The above returns unescaped JSON string representation of .Item.

ternary

The ternary function takes two values, and a test value. If the test value is true, the first value will be returned. If the test value is empty, the second value will be returned. This is similar to the c ternary operator.

true test value

ternary "foo" "bar" true

or

true | ternary "foo" "bar"

The above returns "foo".

false test value

ternary "foo" "bar" false

or

false | ternary "foo" "bar"

The above returns "bar".