From 9497b2cd6f457d61e9dcbfc85d260e4a040edcb3 Mon Sep 17 00:00:00 2001
From: Alisdair McDiarmid <alisdair@users.noreply.github.com>
Date: Mon, 13 Jun 2022 14:33:40 -0400
Subject: [PATCH] json-output: Fix unknowns for tuples and sets

The JSON output for sequences previously omitted unknown values for
tuples and sets, which made it impossible to interpret the corresponding
unknown marks. For example, consider this resource:

    resource "example_resource" "example" {
      tags = toset(["alpha", timestamp(), "charlie"])
    }

This would previously be encoded in JSON as:

    "after": {
        "tags": ["alpha", "charlie"]
    },
    "after_unknown": {
        "id": true,
        "tags": [false, true, false]
    },

That is, the timestamp value would be omitted from the output
altogether, while the corresponding unknown marks would include a value
for each of the set members.

This commit changes the behaviour to:

    "after": {
        "tags": ["alpha", null, "charlie"]
    },
    "after_unknown": {
        "id": true,
        "tags": [false, true, false]
    },

This aligns tuples and sets with the prior behaviour for lists, and
makes it clear which elements are known and which are unknown.
---
 internal/command/jsonplan/plan.go      |  5 +++--
 internal/command/jsonplan/plan_test.go | 13 +++++++++++++
 2 files changed, 16 insertions(+), 2 deletions(-)

diff --git a/internal/command/jsonplan/plan.go b/internal/command/jsonplan/plan.go
index 0a4f9bcd6e..17cc8ad37f 100644
--- a/internal/command/jsonplan/plan.go
+++ b/internal/command/jsonplan/plan.go
@@ -566,8 +566,9 @@ func omitUnknowns(val cty.Value) cty.Value {
 			newVal := omitUnknowns(v)
 			if newVal != cty.NilVal {
 				vals = append(vals, newVal)
-			} else if newVal == cty.NilVal && ty.IsListType() {
-				// list length may be significant, so we will turn unknowns into nulls
+			} else if newVal == cty.NilVal {
+				// element order is how we correlate unknownness, so we must
+				// replace unknowns with nulls
 				vals = append(vals, cty.NullVal(v.Type()))
 			}
 		}
diff --git a/internal/command/jsonplan/plan_test.go b/internal/command/jsonplan/plan_test.go
index 3c640cf6da..ef5b6cda24 100644
--- a/internal/command/jsonplan/plan_test.go
+++ b/internal/command/jsonplan/plan_test.go
@@ -65,6 +65,18 @@ func TestOmitUnknowns(t *testing.T) {
 				"hello": cty.True,
 			}),
 		},
+		{
+			cty.TupleVal([]cty.Value{
+				cty.StringVal("alpha"),
+				cty.UnknownVal(cty.String),
+				cty.StringVal("charlie"),
+			}),
+			cty.TupleVal([]cty.Value{
+				cty.StringVal("alpha"),
+				cty.NullVal(cty.String),
+				cty.StringVal("charlie"),
+			}),
+		},
 		{
 			cty.SetVal([]cty.Value{
 				cty.StringVal("dev"),
@@ -76,6 +88,7 @@ func TestOmitUnknowns(t *testing.T) {
 				cty.StringVal("dev"),
 				cty.StringVal("foo"),
 				cty.StringVal("stg"),
+				cty.NullVal(cty.String),
 			}),
 		},
 		{