External Templates

ent accepts external Go templates to execute using the --template flag. If the template name already defined by ent, it will override the existing one. Otherwise, it will write the execution output to a file with the same name as the template. For example:

stringer.tmpl - This template example will be written in a file named: ent/stringer.go.

{{ define "stringer" }}

{{/* Add the base header for the generated file */}}
{{ $pkg := base $.Config.Package }}
{{ template "header" $ }}

{{/* Loop over all nodes and add implement the "GoStringer" interface */}}
{{ range $n := $.Nodes }}
    {{ $receiver := $n.Receiver }}
    func ({{ $receiver }} *{{ $n.Name }}) GoString() string {
        if {{ $receiver }} == nil {
            return fmt.Sprintf("{{ $n.Name }}(nil)")
        }
        return {{ $receiver }}.String()
    }
{{ end }}

{{ end }}

debug.tmpl - This template example will be written in a file named: ent/debug.go.

{{ define "debug" }}

{{/* A template that adds the functionality for running each client <T> in debug mode */}}

{{/* Add the base header for the generated file */}}
{{ $pkg := base $.Config.Package }}
{{ template "header" $ }}

{{/* Loop over all nodes and add option the "Debug" method */}}
{{ range $n := $.Nodes }}
    {{ $client := print $n.Name "Client" }}
    func (c *{{ $client }}) Debug() *{{ $client }} {
        if c.debug {
            return c
        }
        cfg := config{driver: dialect.Debug(c.driver, c.log), log: c.log, debug: true, hooks: c.hooks}
        return &{{ $client }}{config: cfg}
    }
{{ end }}

{{ end }}

In order to override an existing template, use its name. For example:

{{/* A template for adding additional fields to specific types. */}}
{{ define "model/fields/additional" }}
    {{- /* Add static fields to the "Card" entity. */}}
    {{- if eq $.Name "Card" }}
        // StaticField defined by templates.
        StaticField string `json:"static_field,omitempty"`
    {{- end }}
{{ end }}

Annotations

Schema annotations allow attaching metadata to fields and edges and inject them to external templates.
An annotation must be a Go type that is serializable to JSON raw value (e.g. struct, map or slice) and implement the Annotation interface.

Here's an example of an annotation and its usage in schema and template:

1. An annotation definition:

package entgql

// Annotation annotates fields with metadata for templates.
type Annotation struct {
    // OrderField is the ordering field as defined in graphql schema.
    OrderField string
}

// Name implements ent.Annotation interface.
func (Annotation) Name() string {
    return "EntGQL"
}

2. Annotation usage in ent/schema:

// User schema.
type User struct {
    ent.Schema
}

// Fields of the user.
func (User) Fields() []ent.Field {
    return []ent.Field{
        field.Time("creation_date").
            Annotations(entgql.Annotation{
                OrderField: "CREATED_AT",
            }),
    }
}

3. Annotation usage in external template:

{{ range $node := $.Nodes }}
    {{ range $f := $node.Fields }}
        {{/* Get the annotation by its name. See: Annotation.Name */}}
        {{ if $annotation := $f.Annotations.EntGQL }}
            {{/* Get the field from the annotation. */}}
            {{ $orderField := $annotation.OrderField }}
        {{ end }}
    {{ end }}
{{ end }}

Examples

• A custom template for implementing the Node API for GraphQL - Github.

• An example for executing external templates with custom functions. See configuration and its README file.

Documentation

Templates are executed on either a specific node-type or the entire schema graph. For API documentation, see the GoDoc.