terraform/config/raw_config.go

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package config
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import (
"bytes"
"encoding/gob"
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"github.com/mitchellh/copystructure"
"github.com/mitchellh/reflectwalk"
)
// UnknownVariableValue is a sentinel value that can be used
// to denote that the value of a variable is unknown at this time.
// RawConfig uses this information to build up data about
// unknown keys.
const UnknownVariableValue = "74D93920-ED26-11E3-AC10-0800200C9A66"
// RawConfig is a structure that holds a piece of configuration
// where te overall structure is unknown since it will be used
// to configure a plugin or some other similar external component.
//
// RawConfigs can be interpolated with variables that come from
// other resources, user variables, etc.
//
// RawConfig supports a query-like interface to request
// information from deep within the structure.
type RawConfig struct {
Key string
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Raw map[string]interface{}
Interpolations []Interpolation
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Variables map[string]InterpolatedVariable
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config map[string]interface{}
unknownKeys []string
}
// NewRawConfig creates a new RawConfig structure and populates the
// publicly readable struct fields.
func NewRawConfig(raw map[string]interface{}) (*RawConfig, error) {
result := &RawConfig{Raw: raw}
if err := result.init(); err != nil {
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return nil, err
}
return result, nil
}
// Value returns the value of the configuration if this configuration
// has a Key set. If this does not have a Key set, nil will be returned.
func (r *RawConfig) Value() interface{} {
if c := r.Config(); c != nil {
if v, ok := c[r.Key]; ok {
return v
}
}
return r.Raw[r.Key]
}
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// Config returns the entire configuration with the variables
// interpolated from any call to Interpolate.
//
// If any interpolated variables are unknown (value set to
// UnknownVariableValue), the first non-container (map, slice, etc.) element
// will be removed from the config. The keys of unknown variables
// can be found using the UnknownKeys function.
//
// By pruning out unknown keys from the configuration, the raw
// structure will always successfully decode into its ultimate
// structure using something like mapstructure.
func (r *RawConfig) Config() map[string]interface{} {
return r.config
}
// Interpolate uses the given mapping of variable values and uses
// those as the values to replace any variables in this raw
// configuration.
//
// Any prior calls to Interpolate are replaced with this one.
//
// If a variable key is missing, this will panic.
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func (r *RawConfig) Interpolate(vs map[string]string) error {
config, err := copystructure.Copy(r.Raw)
if err != nil {
return err
}
r.config = config.(map[string]interface{})
fn := func(i Interpolation) (string, error) {
return i.Interpolate(vs)
}
w := &interpolationWalker{F: fn, Replace: true}
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err = reflectwalk.Walk(r.config, w)
if err != nil {
return err
}
r.unknownKeys = w.unknownKeys
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return nil
}
func (r *RawConfig) init() error {
r.config = r.Raw
r.Interpolations = nil
r.Variables = nil
fn := func(i Interpolation) (string, error) {
r.Interpolations = append(r.Interpolations, i)
for k, v := range i.Variables() {
if r.Variables == nil {
r.Variables = make(map[string]InterpolatedVariable)
}
r.Variables[k] = v
}
return "", nil
}
walker := &interpolationWalker{F: fn}
if err := reflectwalk.Walk(r.Raw, walker); err != nil {
return err
}
return nil
}
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func (r *RawConfig) merge(r2 *RawConfig) *RawConfig {
rawRaw, err := copystructure.Copy(r.Raw)
if err != nil {
panic(err)
}
raw := rawRaw.(map[string]interface{})
for k, v := range r2.Raw {
raw[k] = v
}
result, err := NewRawConfig(raw)
if err != nil {
panic(err)
}
return result
}
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// UnknownKeys returns the keys of the configuration that are unknown
// because they had interpolated variables that must be computed.
func (r *RawConfig) UnknownKeys() []string {
return r.unknownKeys
}
// See GobEncode
func (r *RawConfig) GobDecode(b []byte) error {
err := gob.NewDecoder(bytes.NewReader(b)).Decode(&r.Raw)
if err != nil {
return err
}
return r.init()
}
// GobEncode is a custom Gob encoder to use so that we only include the
// raw configuration. Interpolated variables and such are lost and the
// tree of interpolated variables is recomputed on decode, since it is
// referentially transparent.
func (r *RawConfig) GobEncode() ([]byte, error) {
var buf bytes.Buffer
if err := gob.NewEncoder(&buf).Encode(r.Raw); err != nil {
return nil, err
}
return buf.Bytes(), nil
}