packer-cn/template/interpolate/i.go

69 lines
1.6 KiB
Go

package interpolate
import (
"bytes"
"text/template"
)
// Context is the context that an interpolation is done in. This defines
// things such as available variables.
type Context struct {
// Data is the data for the template that is available
Data interface{}
// Funcs are extra functions available in the template
Funcs map[string]interface{}
// UserVariables is the mapping of user variables that the
// "user" function reads from.
UserVariables map[string]string
// EnableEnv enables the env function
EnableEnv bool
}
// Render is shorthand for constructing an I and calling Render.
func Render(v string, ctx *Context) (string, error) {
return (&I{Value: v}).Render(ctx)
}
// Validate is shorthand for constructing an I and calling Validate.
func Validate(v string, ctx *Context) error {
return (&I{Value: v}).Validate(ctx)
}
// I stands for "interpolation" and is the main interpolation struct
// in order to render values.
type I struct {
Value string
}
// Render renders the interpolation with the given context.
func (i *I) Render(ctx *Context) (string, error) {
tpl, err := i.template(ctx)
if err != nil {
return "", err
}
var result bytes.Buffer
var data interface{}
if ctx != nil {
data = ctx.Data
}
if err := tpl.Execute(&result, data); err != nil {
return "", err
}
return result.String(), nil
}
// Validate validates that the template is syntactically valid.
func (i *I) Validate(ctx *Context) error {
_, err := i.template(ctx)
return err
}
func (i *I) template(ctx *Context) (*template.Template, error) {
return template.New("root").Funcs(Funcs(ctx)).Parse(i.Value)
}