Metago documentation

Template helpers

Metago includes standard Go template functions plus helpers for metadata, names, tags, properties, types, imports, and collections.

Metadata

Helper	Result
`name .`	Name of an invocation, type, field, method, or value.
`typeof .`	Underlying or field type.
`keys .`	Field names, or sorted map keys.
`fieldNames .`	Target field names.
`methodNames .`	Comma-separated method names.

Struct tags

For ID int \json:“id,omitempty”``:

Helper	Result
`tag . "json"`	`id,omitempty`
`tagName . "json"`	`id`
`tagOpts . "json"`	Options after the first comma.
`tagHas . "json" "omitempty"`	Whether the option exists.
`tagExists . "json"`	Whether the tag key exists.

Properties

Helper	Result
`prop . "validate" "max"`	A named property value, or empty string.
`props . "validate"`	The complete group with `.Args` and `.Argv`.
`propHas . "validate" "required"`	Whether a bare flag exists.
`propExists . "pii"`	Whether the namespace exists.

These accept fields, types, methods, functions, and invocations.

Field filters

fieldsWithTag, fieldsWithoutTag, exportedFields, unexportedFields, embeddedFields, and nonEmbeddedFields accept an invocation, .Type, or a field slice.

{{ range exportedFields (fieldsWithTag . "json") }}
    {{ name . }}
{{ end }}

Naming

Helper	Example
`snake .Name`	`UserID` → `user_id`
`kebab .Name`	`UserID` → `user-id`
`camel .Name`	`user_id` → `userID`
`pascal .Name`	`user_id` → `UserID`
`initial .Name`	`User` → `u`
`receiver .`	`UserProfile` → `up`
`exported .Name`	Tests exported visibility.
`unexported .Name`	Lowercases the first rune.

Strings

lower, upper, contains, hasPrefix, hasSuffix, trimPrefix, trimSuffix, replace, split, join, and quote provide common string operations. quote emits a safe Go string literal.

Types

Use isString, isInt, isBool, isFloat, isSlice, isMap, and isPointer for branches. elem returns the element of []T or *T; zero returns a Go zero value.

{{ if isPointer . }}
if value == nil { return {{ zero (elem .) }} }
{{ end }}

Data

Helper	Purpose
`dict "k" v`	Create a map.
`list "a" "b"`	Create a list.
`get m "key"`	Read a map key or exported struct field.
`arg 0`, `arg "key"`	Read directive arguments.
`default fallback value`	Replace a zero value.