[WIP] Add a diff option to a plan command

[bells17]

Hi, Could I append diff option to plan command?
I want to use this file to analyze the diff.

generated example is below:

{
  "Modules": [
    {
      "Path": [
        "root"
      ],
      "Resources": {
        "aws_security_group.sample": {
          "Attributes": {
            "revoke_rules_on_delete": {
              "Old": "",
              "New": "true",
              "NewComputed": false,
              "NewRemoved": false,
              "NewExtra": null,
              "RequiresNew": false,
              "Sensitive": false,
              "Type": 0
            },
            "tags.%": {
              "Old": "0",
              "New": "1",
              "NewComputed": false,
              "NewRemoved": false,
              "NewExtra": null,
              "RequiresNew": false,
              "Sensitive": false,
              "Type": 0
            },
            "tags.Name": {
              "Old": "",
              "New": "sample",
              "NewComputed": false,
              "NewRemoved": false,
              "NewExtra": null,
              "RequiresNew": false,
              "Sensitive": false,
              "Type": 0
            }
          },
          "Destroy": false,
          "DestroyDeposed": false,
          "DestroyTainted": false,
          "Meta": null
        }
      },
      "Destroy": false
    }
  ]
}

test result

$ go test -v -run='TestLocal_plan*' -timeout=60s -parallel=4 github.com/hashicorp/terraform/backend/local
=== RUN   TestLocal_planBasic
--- PASS: TestLocal_planBasic (0.00s)
=== RUN   TestLocal_planInAutomation
--- PASS: TestLocal_planInAutomation (0.00s)
=== RUN   TestLocal_planNoConfig
--- PASS: TestLocal_planNoConfig (0.00s)
=== RUN   TestLocal_planRefreshFalse
--- PASS: TestLocal_planRefreshFalse (0.00s)
=== RUN   TestLocal_planDestroy
--- PASS: TestLocal_planDestroy (0.00s)
=== RUN   TestLocal_planOutPathNoChange
--- PASS: TestLocal_planOutPathNoChange (0.00s)
=== RUN   TestLocal_planDiff
--- PASS: TestLocal_planDiff (0.00s)
=== RUN   TestLocal_planScaleOutNoDupeCount
--- PASS: TestLocal_planScaleOutNoDupeCount (0.01s)
PASS
ok    github.com/hashicorp/terraform/backend/local  0.047s

[apparentlymart]

Hi @bells17,

As previously discussed in #10665 (which I contributed before I was a HashiCorp employee), we're intentionally not supporting machine-readable plans at this time because we expect to need to change the representation of plans to support forthcoming features and so we're not yet ready to commit to compatibility on a specific JSON format.

In the mean time, you may be able to do what you want by using Terraform as a library from your own Go program and calling terraform.ReadPlan. We cannot promise that this interface will not change in future versions -- in fact, it definitely will change at least once during our current work to change the internal representation of values -- but if you are willing to accept a small amount of gradual maintenance here then this could get you what you want in the short term.

We do plan to have a machine-readable plan description in the long run, once we've completed all of the expected work that will require changes to the format. However, we're not ready to move forward with that for the moment.

I'm sorry to have to say no to this for now, and I'm grateful for the time you spent on this work. Possibly we can build on this in future when the time is right to implement machine-readable plans.

[bells17]

Hi, @apparentlymart,

Thank you for reviewing, and teaching me about the previously discussed.
I think create a diff output tool with the Terraform Go API for analyze a diff.

but if you'll ready supporting machine-readable plans, I use this.
Thanks!

[ghost]

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