opentofu/internal/command/state_show.go
Martin Atkins 89b05050ec core: Functional-style API for terraform.Context
Previously terraform.Context was built in an unfortunate way where all of
the data was provided up front in terraform.NewContext and then mutated
directly by subsequent operations. That made the data flow hard to follow,
commonly leading to bugs, and also meant that we were forced to take
various actions too early in terraform.NewContext, rather than waiting
until a more appropriate time during an operation.

This (enormous) commit changes terraform.Context so that its fields are
broadly just unchanging data about the execution context (current
workspace name, available plugins, etc) whereas the main data Terraform
works with arrives via individual method arguments and is returned in
return values.

Specifically, this means that terraform.Context no longer "has-a" config,
state, and "planned changes", instead holding on to those only temporarily
during an operation. The caller is responsible for propagating the outcome
of one step into the next step so that the data flow between operations is
actually visible.

However, since that's a change to the main entry points in the "terraform"
package, this commit also touches every file in the codebase which
interacted with those APIs. Most of the noise here is in updating tests
to take the same actions using the new API style, but this also affects
the main-code callers in the backends and in the command package.

My goal here was to refactor without changing observable behavior, but in
practice there are a couple externally-visible behavior variations here
that seemed okay in service of the broader goal:
 - The "terraform graph" command is no longer hooked directly into the
   core graph builders, because that's no longer part of the public API.
   However, I did include a couple new Context functions whose contract
   is to produce a UI-oriented graph, and _for now_ those continue to
   return the physical graph we use for those operations. There's no
   exported API for generating the "validate" and "eval" graphs, because
   neither is particularly interesting in its own right, and so
   "terraform graph" no longer supports those graph types.
 - terraform.NewContext no longer has the responsibility for collecting
   all of the provider schemas up front. Instead, we wait until we need
   them. However, that means that some of our error messages now have a
   slightly different shape due to unwinding through a differently-shaped
   call stack. As of this commit we also end up reloading the schemas
   multiple times in some cases, which is functionally acceptable but
   likely represents a performance regression. I intend to rework this to
   use caching, but I'm saving that for a later commit because this one is
   big enough already.

The proximal reason for this change is to resolve the chicken/egg problem
whereby there was previously no single point where we could apply "moved"
statements to the previous run state before creating a plan. With this
change in place, we can now do that as part of Context.Plan, prior to
forking the input state into the three separate state artifacts we use
during planning.

However, this is at least the third project in a row where the previous
API design led to piling more functionality into terraform.NewContext and
then working around the incorrect order of operations that produces, so
I intend that by paying the cost/risk of this large diff now we can in
turn reduce the cost/risk of future projects that relate to our main
workflow actions.
2021-08-30 13:59:14 -07:00

185 lines
4.8 KiB
Go

package command
import (
"fmt"
"os"
"strings"
"github.com/hashicorp/terraform/internal/addrs"
"github.com/hashicorp/terraform/internal/backend"
"github.com/hashicorp/terraform/internal/command/format"
"github.com/hashicorp/terraform/internal/states"
"github.com/mitchellh/cli"
)
// StateShowCommand is a Command implementation that shows a single resource.
type StateShowCommand struct {
Meta
StateMeta
}
func (c *StateShowCommand) Run(args []string) int {
args = c.Meta.process(args)
cmdFlags := c.Meta.defaultFlagSet("state show")
cmdFlags.StringVar(&c.Meta.statePath, "state", "", "path")
if err := cmdFlags.Parse(args); err != nil {
c.Ui.Error(fmt.Sprintf("Error parsing command-line flags: %s\n", err.Error()))
return 1
}
args = cmdFlags.Args()
if len(args) != 1 {
c.Ui.Error("Exactly one argument expected.\n")
return cli.RunResultHelp
}
// Check for user-supplied plugin path
var err error
if c.pluginPath, err = c.loadPluginPath(); err != nil {
c.Ui.Error(fmt.Sprintf("Error loading plugin path: %s", err))
return 1
}
// Load the backend
b, backendDiags := c.Backend(nil)
if backendDiags.HasErrors() {
c.showDiagnostics(backendDiags)
return 1
}
// We require a local backend
local, ok := b.(backend.Local)
if !ok {
c.Ui.Error(ErrUnsupportedLocalOp)
return 1
}
// This is a read-only command
c.ignoreRemoteBackendVersionConflict(b)
// Check if the address can be parsed
addr, addrDiags := addrs.ParseAbsResourceInstanceStr(args[0])
if addrDiags.HasErrors() {
c.Ui.Error(fmt.Sprintf(errParsingAddress, args[0]))
return 1
}
// We expect the config dir to always be the cwd
cwd, err := os.Getwd()
if err != nil {
c.Ui.Error(fmt.Sprintf("Error getting cwd: %s", err))
return 1
}
// Build the operation (required to get the schemas)
opReq := c.Operation(b)
opReq.AllowUnsetVariables = true
opReq.ConfigDir = cwd
opReq.ConfigLoader, err = c.initConfigLoader()
if err != nil {
c.Ui.Error(fmt.Sprintf("Error initializing config loader: %s", err))
return 1
}
// Get the context (required to get the schemas)
lr, _, ctxDiags := local.LocalRun(opReq)
if ctxDiags.HasErrors() {
c.showDiagnostics(ctxDiags)
return 1
}
// Get the schemas from the context
schemas, diags := lr.Core.Schemas(lr.Config, lr.InputState)
if diags.HasErrors() {
c.showDiagnostics(diags)
return 1
}
// Get the state
env, err := c.Workspace()
if err != nil {
c.Ui.Error(fmt.Sprintf("Error selecting workspace: %s", err))
return 1
}
stateMgr, err := b.StateMgr(env)
if err != nil {
c.Ui.Error(fmt.Sprintf(errStateLoadingState, err))
return 1
}
if err := stateMgr.RefreshState(); err != nil {
c.Ui.Error(fmt.Sprintf("Failed to refresh state: %s", err))
return 1
}
state := stateMgr.State()
if state == nil {
c.Ui.Error(errStateNotFound)
return 1
}
is := state.ResourceInstance(addr)
if !is.HasCurrent() {
c.Ui.Error(errNoInstanceFound)
return 1
}
// check if the resource has a configured provider, otherwise this will use the default provider
rs := state.Resource(addr.ContainingResource())
absPc := addrs.AbsProviderConfig{
Provider: rs.ProviderConfig.Provider,
Alias: rs.ProviderConfig.Alias,
Module: addrs.RootModule,
}
singleInstance := states.NewState()
singleInstance.EnsureModule(addr.Module).SetResourceInstanceCurrent(
addr.Resource,
is.Current,
absPc,
)
output := format.State(&format.StateOpts{
State: singleInstance,
Color: c.Colorize(),
Schemas: schemas,
})
c.Ui.Output(output[strings.Index(output, "#"):])
return 0
}
func (c *StateShowCommand) Help() string {
helpText := `
Usage: terraform [global options] state show [options] ADDRESS
Shows the attributes of a resource in the Terraform state.
This command shows the attributes of a single resource in the Terraform
state. The address argument must be used to specify a single resource.
You can view the list of available resources with "terraform state list".
Options:
-state=statefile Path to a Terraform state file to use to look
up Terraform-managed resources. By default it will
use the state "terraform.tfstate" if it exists.
`
return strings.TrimSpace(helpText)
}
func (c *StateShowCommand) Synopsis() string {
return "Show a resource in the state"
}
const errNoInstanceFound = `No instance found for the given address!
This command requires that the address references one specific instance.
To view the available instances, use "terraform state list". Please modify
the address to reference a specific instance.`
const errParsingAddress = `Error parsing instance address: %s
This command requires that the address references one specific instance.
To view the available instances, use "terraform state list". Please modify
the address to reference a specific instance.`