terraform/helper/schema/backend.go

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package schema
import (
"context"
"fmt"
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"github.com/hashicorp/terraform/tfdiags"
"github.com/zclconf/go-cty/cty"
"github.com/hashicorp/terraform/configs/configschema"
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"github.com/hashicorp/terraform/configs/hcl2shim"
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"github.com/hashicorp/terraform/terraform"
ctyconvert "github.com/zclconf/go-cty/cty/convert"
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)
// Backend represents a partial backend.Backend implementation and simplifies
// the creation of configuration loading and validation.
//
// Unlike other schema structs such as Provider, this struct is meant to be
// embedded within your actual implementation. It provides implementations
// only for Input and Configure and gives you a method for accessing the
// configuration in the form of a ResourceData that you're expected to call
// from the other implementation funcs.
type Backend struct {
// Schema is the schema for the configuration of this backend. If this
// Backend has no configuration this can be omitted.
Schema map[string]*Schema
// ConfigureFunc is called to configure the backend. Use the
// FromContext* methods to extract information from the context.
// This can be nil, in which case nothing will be called but the
// config will still be stored.
ConfigureFunc func(context.Context) error
config *ResourceData
}
var (
backendConfigKey = contextKey("backend config")
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)
// FromContextBackendConfig extracts a ResourceData with the configuration
// from the context. This should only be called by Backend functions.
func FromContextBackendConfig(ctx context.Context) *ResourceData {
return ctx.Value(backendConfigKey).(*ResourceData)
}
func (b *Backend) ConfigSchema() *configschema.Block {
// This is an alias of CoreConfigSchema just to implement the
// backend.Backend interface.
return b.CoreConfigSchema()
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}
func (b *Backend) PrepareConfig(configVal cty.Value) (cty.Value, tfdiags.Diagnostics) {
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if b == nil {
return configVal, nil
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}
var diags tfdiags.Diagnostics
var err error
// In order to use Transform below, this needs to be filled out completely
// according the schema.
configVal, err = b.CoreConfigSchema().CoerceValue(configVal)
if err != nil {
return configVal, diags.Append(err)
}
// lookup any required, top-level attributes that are Null, and see if we
// have a Default value available.
configVal, err = cty.Transform(configVal, func(path cty.Path, val cty.Value) (cty.Value, error) {
// we're only looking for top-level attributes
if len(path) != 1 {
return val, nil
}
// nothing to do if we already have a value
if !val.IsNull() {
return val, nil
}
// get the Schema definition for this attribute
getAttr, ok := path[0].(cty.GetAttrStep)
// these should all exist, but just ignore anything strange
if !ok {
return val, nil
}
attrSchema := b.Schema[getAttr.Name]
// continue to ignore anything that doesn't match
if attrSchema == nil {
return val, nil
}
// this is deprecated, so don't set it
if attrSchema.Deprecated != "" || attrSchema.Removed != "" {
return val, nil
}
// find a default value if it exists
def, err := attrSchema.DefaultValue()
if err != nil {
diags = diags.Append(fmt.Errorf("error getting default for %q: %s", getAttr.Name, err))
return val, err
}
// no default
if def == nil {
return val, nil
}
// create a cty.Value and make sure it's the correct type
tmpVal := hcl2shim.HCL2ValueFromConfigValue(def)
// helper/schema used to allow setting "" to a bool
if val.Type() == cty.Bool && tmpVal.RawEquals(cty.StringVal("")) {
// return a warning about the conversion
diags = diags.Append("provider set empty string as default value for bool " + getAttr.Name)
tmpVal = cty.False
}
val, err = ctyconvert.Convert(tmpVal, val.Type())
if err != nil {
diags = diags.Append(fmt.Errorf("error setting default for %q: %s", getAttr.Name, err))
}
return val, err
})
if err != nil {
// any error here was already added to the diagnostics
return configVal, diags
}
shimRC := b.shimConfig(configVal)
warns, errs := schemaMap(b.Schema).Validate(shimRC)
for _, warn := range warns {
diags = diags.Append(tfdiags.SimpleWarning(warn))
}
for _, err := range errs {
diags = diags.Append(err)
}
return configVal, diags
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}
func (b *Backend) Configure(obj cty.Value) tfdiags.Diagnostics {
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if b == nil {
return nil
}
var diags tfdiags.Diagnostics
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sm := schemaMap(b.Schema)
shimRC := b.shimConfig(obj)
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// Get a ResourceData for this configuration. To do this, we actually
// generate an intermediary "diff" although that is never exposed.
diff, err := sm.Diff(nil, shimRC, nil, nil, true)
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if err != nil {
diags = diags.Append(err)
return diags
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}
data, err := sm.Data(nil, diff)
if err != nil {
diags = diags.Append(err)
return diags
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}
b.config = data
if b.ConfigureFunc != nil {
err = b.ConfigureFunc(context.WithValue(
context.Background(), backendConfigKey, data))
if err != nil {
diags = diags.Append(err)
return diags
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}
}
return diags
}
// shimConfig turns a new-style cty.Value configuration (which must be of
// an object type) into a minimal old-style *terraform.ResourceConfig object
// that should be populated enough to appease the not-yet-updated functionality
// in this package. This should be removed once everything is updated.
func (b *Backend) shimConfig(obj cty.Value) *terraform.ResourceConfig {
shimMap, ok := hcl2shim.ConfigValueFromHCL2(obj).(map[string]interface{})
if !ok {
// If the configVal was nil, we still want a non-nil map here.
shimMap = map[string]interface{}{}
}
return &terraform.ResourceConfig{
Config: shimMap,
Raw: shimMap,
}
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}
// Config returns the configuration. This is available after Configure is
// called.
func (b *Backend) Config() *ResourceData {
return b.config
}