support deprecating variables

Author: DanielMSchmidt

internal/configs/named_values.go

@@ -48,6 +48,10 @@ type Variable struct {
 	Nullable    bool
 	NullableSet bool
 
+	Deprecated      string
+	DeprecatedSet   bool
+	DeprecatedRange hcl.Range
+
 	DeclRange hcl.Range
 }
 
@@ -186,6 +190,13 @@ func decodeVariableBlock(block *hcl.Block, override bool) (*Variable, hcl.Diagno
 		v.Default = val
 	}
 
+	if attr, exists := content.Attributes["deprecated"]; exists {
+		valDiags := gohcl.DecodeExpression(attr.Expr, nil, &v.Deprecated)
+		diags = append(diags, valDiags...)
+		v.DeprecatedSet = true
+		v.DeprecatedRange = attr.Range
+	}
+
 	for _, block := range content.Blocks {
 		switch block.Type {
 
@@ -499,6 +510,9 @@ var variableBlockSchema = &hcl.BodySchema{
 		{
 			Name: "nullable",
 		},
+		{
+			Name: "deprecated",
+		},
 	},
 	Blocks: []hcl.BlockHeaderSchema{
 		{

internal/configs/named_values_test.go

@@ -48,3 +48,30 @@ func TestVariableInvalidDefault(t *testing.T) {
 		}
 	}
 }
+
+func TestVariableDeprecation(t *testing.T) {
+	src := `
+		variable "foo" {
+			type = string
+			deprecated = "This variable is deprecated, use bar instead"
+		}
+	`
+
+	hclF, diags := hclsyntax.ParseConfig([]byte(src), "test.tf", hcl.InitialPos)
+	if diags.HasErrors() {
+		t.Fatal(diags.Error())
+	}
+
+	b, diags := parseConfigFile(hclF.Body, nil, false, false)
+	if diags.HasErrors() {
+		t.Fatalf("unexpected error: %q", diags)
+	}
+
+	if !b.Variables[0].DeprecatedSet {
+		t.Fatalf("expected variable to be deprecated")
+	}
+
+	if b.Variables[0].Deprecated != "This variable is deprecated, use bar instead" {
+		t.Fatalf("expected variable to have deprecation message")
+	}
+}

internal/terraform/context_plan2_test.go

@@ -6068,3 +6068,130 @@ data "test_data_source" "foo" {
 	_, diags := ctx.Plan(m, states.NewState(), SimplePlanOpts(plans.NormalMode, testInputValuesUnset(m.Module.Variables)))
 	assertNoErrors(t, diags)
 }
+
+func TestContext2Plan_deprecated_variable(t *testing.T) {
+	m := testModuleInline(t, map[string]string{
+		"mod/main.tf": `
+variable "old-and-used" {
+	type = string
+	deprecated = "module variable deprecation"
+	default = "optional"
+}
+
+variable "old-and-unused" {
+	type = string
+	deprecated = "module variable deprecation"
+	default = "optional"
+}
+
+variable "new" {
+    type = string
+    default = "optional"
+}
+
+output "use-everything" {
+    value = {
+      used = var.old-and-used
+      unused = var.old-and-unused
+      new = var.new
+    }
+}
+`,
+		"main.tf": `
+variable "root-old-and-used" {
+	type = string
+	deprecated = "root variable deprecation"
+	default = "optional"
+}
+
+variable "root-old-and-unused" {
+	type = string
+	deprecated = "root variable deprecation"
+	default = "optional"
+}
+
+variable "new" {
+    type = string
+    default = "new"
+}
+
+module "old-mod" {
+    source = "./mod"
+    old-and-used = "old"
+}
+
+module "new-mod" {
+    source = "./mod"
+    new = "new"
+}
+
+output "use-everything" {
+    value = {
+      used = var.root-old-and-used
+      unused = var.root-old-and-unused
+      new = var.new
+    }
+}
+`,
+	})
+
+	p := new(testing_provider.MockProvider)
+	p.GetProviderSchemaResponse = getProviderSchemaResponseFromProviderSchema(&providerSchema{
+		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),
+		},
+	})
+
+	vars := InputValues{
+		"root-old-and-used": {
+			Value: cty.StringVal("root-old-and-used"),
+		},
+		"root-old-and-unused": {
+			Value: cty.NullVal(cty.String),
+		},
+		"new": {
+			Value: cty.StringVal("new"),
+		},
+	}
+
+	_, diags := ctx.Plan(m, states.NewState(), SimplePlanOpts(plans.NormalMode, vars))
+
+	var expectedDiags tfdiags.Diagnostics
+	expectedDiags = expectedDiags.Append(
+		&hcl.Diagnostic{
+			Severity: hcl.DiagWarning,
+			Summary:  "Usage of deprecated variable",
+			Detail:   "root variable deprecation",
+			Subject: &hcl.Range{
+				Filename: filepath.Join(m.Module.SourceDir, "main.tf"),
+				Start:    hcl.Pos{Line: 4, Column: 2, Byte: 48},
+				End:      hcl.Pos{Line: 4, Column: 42, Byte: 88},
+			},
+		},
+		&hcl.Diagnostic{
+			Severity: hcl.DiagWarning,
+			Summary:  "Usage of deprecated variable",
+			Detail:   "module variable deprecation",
+			Subject: &hcl.Range{
+				Filename: filepath.Join(m.Module.SourceDir, "main.tf"),
+				Start:    hcl.Pos{Line: 21, Column: 20, Byte: 346},
+				End:      hcl.Pos{Line: 21, Column: 25, Byte: 351},
+			},
+		},
+	)
+
+	assertDiagnosticsMatch(t, diags, expectedDiags)
+}

internal/terraform/node_module_variable.go

@@ -309,6 +309,15 @@ func (n *nodeModuleVariable) evalModuleVariable(ctx EvalContext, validateOnly bo
 	finalVal, moreDiags := prepareFinalInputVariableValue(n.Addr, rawVal, n.Config)
 	diags = diags.Append(moreDiags)
 
+	if n.Config.DeprecatedSet && givenVal.IsWhollyKnown() && !givenVal.IsNull() && validateOnly {
+		diags = diags.Append(&hcl.Diagnostic{
+			Severity: hcl.DiagWarning,
+			Summary:  "Usage of deprecated variable",
+			Detail:   n.Config.Deprecated,
+			Subject:  n.Expr.Range().Ptr(),
+		})
+	}
+
 	return finalVal, diags.ErrWithWarnings()
 }
 

internal/terraform/node_root_variable.go

@@ -92,6 +92,15 @@ func (n *NodeRootVariable) Execute(ctx EvalContext, op walkOperation) tfdiags.Di
 		}
 	}
 
+	if n.Config.DeprecatedSet && givenVal.Value.IsWhollyKnown() && !givenVal.Value.IsNull() && op == walkPlan {
+		diags = diags.Append(&hcl.Diagnostic{
+			Severity: hcl.DiagWarning,
+			Summary:  "Usage of deprecated variable",
+			Detail:   n.Config.Deprecated,
+			Subject:  &n.Config.DeprecatedRange,
+		})
+	}
+
 	if n.Planning {
 		if checkState := ctx.Checks(); checkState.ConfigHasChecks(n.Addr.InModule(addrs.RootModule)) {
 			ctx.Checks().ReportCheckableObjects(