terraform/internal/plans/planfile/reader.go

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package planfile
import (
"archive/zip"
"bytes"
"fmt"
"io/ioutil"
"github.com/hashicorp/terraform/internal/configs"
"github.com/hashicorp/terraform/internal/configs/configload"
"github.com/hashicorp/terraform/internal/plans"
"github.com/hashicorp/terraform/internal/states/statefile"
"github.com/hashicorp/terraform/internal/tfdiags"
)
const tfstateFilename = "tfstate"
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const tfstatePreviousFilename = "tfstate-prev"
// Reader is the main type used to read plan files. Create a Reader by calling
// Open.
//
// A plan file is a random-access file format, so methods of Reader must
// be used to access the individual portions of the file for further
// processing.
type Reader struct {
zip *zip.ReadCloser
}
// Open creates a Reader for the file at the given filename, or returns an
// error if the file doesn't seem to be a planfile.
func Open(filename string) (*Reader, error) {
r, err := zip.OpenReader(filename)
if err != nil {
// To give a better error message, we'll sniff to see if this looks
// like our old plan format from versions prior to 0.12.
if b, sErr := ioutil.ReadFile(filename); sErr == nil {
if bytes.HasPrefix(b, []byte("tfplan")) {
return nil, fmt.Errorf("the given plan file was created by an earlier version of Terraform; plan files cannot be shared between different Terraform versions")
}
}
return nil, err
}
// Sniff to make sure this looks like a plan file, as opposed to any other
// random zip file the user might have around.
var planFile *zip.File
for _, file := range r.File {
if file.Name == tfplanFilename {
planFile = file
break
}
}
if planFile == nil {
return nil, fmt.Errorf("the given file is not a valid plan file")
}
// For now, we'll just accept the presence of the tfplan file as enough,
// and wait to validate the version when the caller requests the plan
// itself.
return &Reader{
zip: r,
}, nil
}
// ReadPlan reads the plan embedded in the plan file.
//
// Errors can be returned for various reasons, including if the plan file
// is not of an appropriate format version, if it was created by a different
// version of Terraform, if it is invalid, etc.
func (r *Reader) ReadPlan() (*plans.Plan, error) {
var planFile *zip.File
for _, file := range r.zip.File {
if file.Name == tfplanFilename {
planFile = file
break
}
}
if planFile == nil {
// This should never happen because we checked for this file during
// Open, but we'll check anyway to be safe.
return nil, fmt.Errorf("the plan file is invalid")
}
pr, err := planFile.Open()
if err != nil {
return nil, fmt.Errorf("failed to retrieve plan from plan file: %s", err)
}
defer pr.Close()
// There's a slight mismatch in how plans.Plan is modeled vs. how
// the underlying plan file format works, because the "tfplan" embedded
// file contains only some top-level metadata and the planned changes,
// and not the previous run or prior states. Therefore we need to
// build this up in multiple steps.
// This is some technical debt because historically we considered the
// planned changes and prior state as totally separate, but later realized
// that it made sense for a plans.Plan to include the prior state directly
// so we can see what state the plan applies to. Hopefully later we'll
// clean this up some more so that we don't have two different ways to
// access the prior state (this and the ReadStateFile method).
ret, err := readTfplan(pr)
if err != nil {
return nil, err
}
prevRunStateFile, err := r.ReadPrevStateFile()
if err != nil {
return nil, fmt.Errorf("failed to read previous run state from plan file: %s", err)
}
priorStateFile, err := r.ReadStateFile()
if err != nil {
return nil, fmt.Errorf("failed to read prior state from plan file: %s", err)
}
ret.PrevRunState = prevRunStateFile.State
ret.PriorState = priorStateFile.State
return ret, nil
}
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// ReadStateFile reads the state file embedded in the plan file, which
// represents the "PriorState" as defined in plans.Plan.
//
// If the plan file contains no embedded state file, the returned error is
// statefile.ErrNoState.
func (r *Reader) ReadStateFile() (*statefile.File, error) {
for _, file := range r.zip.File {
if file.Name == tfstateFilename {
r, err := file.Open()
if err != nil {
return nil, fmt.Errorf("failed to extract state from plan file: %s", err)
}
return statefile.Read(r)
}
}
return nil, statefile.ErrNoState
}
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// ReadPrevStateFile reads the previous state file embedded in the plan file, which
// represents the "PrevRunState" as defined in plans.Plan.
//
// If the plan file contains no embedded previous state file, the returned error is
// statefile.ErrNoState.
func (r *Reader) ReadPrevStateFile() (*statefile.File, error) {
for _, file := range r.zip.File {
if file.Name == tfstatePreviousFilename {
r, err := file.Open()
if err != nil {
return nil, fmt.Errorf("failed to extract previous state from plan file: %s", err)
}
return statefile.Read(r)
}
}
return nil, statefile.ErrNoState
}
// ReadConfigSnapshot reads the configuration snapshot embedded in the plan
// file.
//
// This is a lower-level alternative to ReadConfig that just extracts the
// source files, without attempting to parse them.
func (r *Reader) ReadConfigSnapshot() (*configload.Snapshot, error) {
return readConfigSnapshot(&r.zip.Reader)
}
// ReadConfig reads the configuration embedded in the plan file.
//
// Internally this function delegates to the configs/configload package to
// parse the embedded configuration and so it returns diagnostics (rather than
// a native Go error as with other methods on Reader).
func (r *Reader) ReadConfig() (*configs.Config, tfdiags.Diagnostics) {
var diags tfdiags.Diagnostics
snap, err := r.ReadConfigSnapshot()
if err != nil {
diags = diags.Append(tfdiags.Sourceless(
tfdiags.Error,
"Failed to read configuration from plan file",
fmt.Sprintf("The configuration file snapshot in the plan file could not be read: %s.", err),
))
return nil, diags
}
loader := configload.NewLoaderFromSnapshot(snap)
rootDir := snap.Modules[""].Dir // Root module base directory
config, configDiags := loader.LoadConfig(rootDir)
diags = diags.Append(configDiags)
return config, diags
}
// Close closes the file, after which no other operations may be performed.
func (r *Reader) Close() error {
return r.zip.Close()
}