test multi-instance postcondition self eval

internal/terraform/context_plan2_test.go

@@ -5955,3 +5955,60 @@ output "staying" {
 		t.Fatalf("unexpected changes: %s", diff)
 	}
 }
+
+func TestContext2Plan_multiInstanceSelfRef(t *testing.T) {
+	// The postcondition here references self, but because instances are
+	// processed concurrently some instances may not be registered yet during
+	// evaluation. This should still evaluate without error, because we know our
+	// self value exists.
+	m := testModuleInline(t, map[string]string{
+		"main.tf": `
+resource "test_resource" "test" {
+}
+
+data "test_data_source" "foo" {
+  count = 100
+  lifecycle {
+    postcondition {
+      condition = self.attr == null
+      error_message = "error"
+    }
+  }
+  depends_on = [test_resource.test]
+}
+`,
+	})
+
+	p := new(testing_provider.MockProvider)
+	p.GetProviderSchemaResponse = getProviderSchemaResponseFromProviderSchema(&providerSchema{
+		DataSources: map[string]*configschema.Block{
+			"test_data_source": {
+				Attributes: map[string]*configschema.Attribute{
+					"attr": {
+						Type:     cty.String,
+						Computed: true,
+					},
+				},
+			},
+		},
+		ResourceTypes: map[string]*configschema.Block{
+			"test_resource": {
+				Attributes: map[string]*configschema.Attribute{
+					"attr": {
+						Type:     cty.String,
+						Computed: true,
+					},
+				},
+			},
+		},
+	})
+
+	ctx := testContext2(t, &ContextOpts{
+		Providers: map[addrs.Provider]providers.Factory{
+			addrs.NewDefaultProvider("test"): testProviderFuncFixed(p),
+		},
+	})
+
+	_, diags := ctx.Plan(m, states.NewState(), SimplePlanOpts(plans.NormalMode, testInputValuesUnset(m.Module.Variables)))
+	assertNoErrors(t, diags)
+}