Add hclext.BoundExpr (#205)

Author: wata727

hclext/expression.go

@@ -0,0 +1,47 @@
+package hclext
+
+import (
+	"github.com/hashicorp/hcl/v2"
+	"github.com/zclconf/go-cty/cty"
+)
+
+// BoundExpr represents an expression whose a value is bound.
+// This is a wrapper for any expression, typically satisfying
+// an interface to behave like the wrapped expression.
+//
+// The difference is that when resolving a value with `Value()`,
+// instead of resolving the variables with EvalContext,
+// the bound value is returned directly.
+type BoundExpr struct {
+	Val cty.Value
+
+	original hcl.Expression
+}
+
+var _ hcl.Expression = (*BoundExpr)(nil)
+
+// BindValue binds the passed value to an expression.
+// This returns the bound expression.
+func BindValue(val cty.Value, expr hcl.Expression) hcl.Expression {
+	return &BoundExpr{original: expr, Val: val}
+}
+
+// Value returns the bound value.
+func (e BoundExpr) Value(*hcl.EvalContext) (cty.Value, hcl.Diagnostics) {
+	return e.Val, nil
+}
+
+// Variables delegates to the wrapped expression.
+func (e BoundExpr) Variables() []hcl.Traversal {
+	return e.original.Variables()
+}
+
+// Range delegates to the wrapped expression.
+func (e BoundExpr) Range() hcl.Range {
+	return e.original.Range()
+}
+
+// StartRange delegates to the wrapped expression.
+func (e BoundExpr) StartRange() hcl.Range {
+	return e.original.StartRange()
+}

plugin/fromproto/fromproto.go

@@ -8,6 +8,8 @@ import (
 	"github.com/terraform-linters/tflint-plugin-sdk/hclext"
 	"github.com/terraform-linters/tflint-plugin-sdk/plugin/proto"
 	"github.com/terraform-linters/tflint-plugin-sdk/tflint"
+	"github.com/zclconf/go-cty/cty"
+	"github.com/zclconf/go-cty/cty/msgpack"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/status"
 )
@@ -62,7 +64,13 @@ func BodyContent(body *proto.BodyContent) (*hclext.BodyContent, hcl.Diagnostics)
 
 	attributes := hclext.Attributes{}
 	for key, attr := range body.Attributes {
-		expr, exprDiags := hclext.ParseExpression(attr.Expr, attr.ExprRange.Filename, Pos(attr.ExprRange.Start))
+		var expr hcl.Expression
+		var exprDiags hcl.Diagnostics
+		if attr.Expression != nil {
+			expr, exprDiags = Expression(attr.Expression)
+		} else {
+			expr, exprDiags = hclext.ParseExpression(attr.Expr, attr.ExprRange.Filename, Pos(attr.ExprRange.Start))
+		}
 		diags = diags.Extend(exprDiags)
 
 		attributes[key] = &hclext.Attribute{
@@ -146,6 +154,22 @@ func Rule(rule *proto.EmitIssue_Rule) *RuleObject {
 	}
 }
 
+// Expression converts proto.Expression to hcl.Expression
+func Expression(expr *proto.Expression) (hcl.Expression, hcl.Diagnostics) {
+	parsed, diags := hclext.ParseExpression(expr.Bytes, expr.Range.Filename, Pos(expr.Range.Start))
+	if diags.HasErrors() {
+		return nil, diags
+	}
+	if expr.Value != nil {
+		val, err := msgpack.Unmarshal(expr.Value, cty.DynamicPseudoType)
+		if err != nil {
+			panic(fmt.Errorf("cannot unmarshal the bound expr: %w", err))
+		}
+		parsed = hclext.BindValue(val, parsed)
+	}
+	return parsed, diags
+}
+
 // Severity converts proto.EmitIssue_Severity to severity
 func Severity(severity proto.EmitIssue_Severity) tflint.Severity {
 	switch severity {

plugin/plugin2host/client.go

@@ -299,9 +299,10 @@ func (c *GRPCClient) EvaluateExpr(expr hcl.Expression, ret interface{}, opts *tf
 	resp, err := c.Client.EvaluateExpr(
 		context.Background(),
 		&proto.EvaluateExpr_Request{
-			Expr:      expr.Range().SliceBytes(file.Bytes),
-			ExprRange: toproto.Range(expr.Range()),
-			Option:    &proto.EvaluateExpr_Option{Type: tyby, ModuleCtx: toproto.ModuleCtxType(opts.ModuleCtx)},
+			Expr:       expr.Range().SliceBytes(file.Bytes),
+			ExprRange:  toproto.Range(expr.Range()),
+			Expression: toproto.Expression(expr, file.Bytes),
+			Option:     &proto.EvaluateExpr_Option{Type: tyby, ModuleCtx: toproto.ModuleCtxType(opts.ModuleCtx)},
 		},
 	)
 	if err != nil {

plugin/plugin2host/plugin2host_test.go

@@ -546,6 +546,55 @@ volume_size = 10`)
 			},
 			ErrCheck: neverHappend,
 		},
+		{
+			Name: "get content with bound expr",
+			Args: func() (*hclext.BodySchema, *tflint.GetModuleContentOption) {
+				return &hclext.BodySchema{
+					Attributes: []hclext.AttributeSchema{{Name: "value"}},
+				}, nil
+			},
+			ServerImpl: func(schema *hclext.BodySchema, opts tflint.GetModuleContentOption) (*hclext.BodyContent, hcl.Diagnostics) {
+				file := hclFile("test.tf", "value = each.key")
+				attrs, diags := file.Body.JustAttributes()
+				if diags.HasErrors() {
+					return nil, diags
+				}
+				attr := attrs["value"]
+
+				return &hclext.BodyContent{
+					Attributes: hclext.Attributes{
+						"value": {
+							Name:      attr.Name,
+							Expr:      hclext.BindValue(cty.StringVal("bound value"), attr.Expr),
+							Range:     attr.Range,
+							NameRange: attr.NameRange,
+						},
+					},
+					Blocks: hclext.Blocks{},
+				}, nil
+			},
+			Want: func(schema *hclext.BodySchema, opts *tflint.GetModuleContentOption) (*hclext.BodyContent, hcl.Diagnostics) {
+				file := hclFile("test.tf", "value = each.key")
+				attrs, diags := file.Body.JustAttributes()
+				if diags.HasErrors() {
+					return nil, diags
+				}
+				attr := attrs["value"]
+
+				return &hclext.BodyContent{
+					Attributes: hclext.Attributes{
+						"value": {
+							Name:      attr.Name,
+							Expr:      hclext.BindValue(cty.StringVal("bound value"), attr.Expr),
+							Range:     attr.Range,
+							NameRange: attr.NameRange,
+						},
+					},
+					Blocks: hclext.Blocks{},
+				}, nil
+			},
+			ErrCheck: neverHappend,
+		},
 		{
 			Name: "get content with options",
 			Args: func() (*hclext.BodySchema, *tflint.GetModuleContentOption) {
@@ -1537,6 +1586,17 @@ func TestEvaluateExpr(t *testing.T) {
 			GetFileImpl: fileExists,
 			ErrCheck:    neverHappend,
 		},
+		{
+			Name:       "bound expr",
+			Expr:       hclext.BindValue(cty.StringVal("bound value"), hclExpr(`var.foo`)),
+			TargetType: reflect.TypeOf(""),
+			ServerImpl: func(expr hcl.Expression, opts tflint.EvaluateExprOption) (cty.Value, error) {
+				return evalExpr(expr, &hcl.EvalContext{})
+			},
+			Want:        "bound value",
+			GetFileImpl: fileExists,
+			ErrCheck:    neverHappend,
+		},
 		{
 			Name:       "eval with moduleCtx option",
 			Expr:       hclExpr(`1`),

plugin/plugin2host/server.go

@@ -112,17 +112,32 @@ func (s *GRPCServer) GetRuleConfigContent(ctx context.Context, req *proto.GetRul
 
 // EvaluateExpr evals the passed expression based on the type.
 func (s *GRPCServer) EvaluateExpr(ctx context.Context, req *proto.EvaluateExpr_Request) (*proto.EvaluateExpr_Response, error) {
-	if req.Expr == nil {
-		return nil, status.Error(codes.InvalidArgument, "expr should not be null")
-	}
-	if req.ExprRange == nil {
-		return nil, status.Error(codes.InvalidArgument, "expr_range should not be null")
+	if req.Expression == nil {
+		if req.Expr == nil {
+			return nil, status.Error(codes.InvalidArgument, "expr should not be null")
+		}
+		if req.ExprRange == nil {
+			return nil, status.Error(codes.InvalidArgument, "expr_range should not be null")
+		}
+	} else {
+		if req.Expression.Bytes == nil {
+			return nil, status.Error(codes.InvalidArgument, "expression.bytes should not be null")
+		}
+		if req.Expression.Range == nil {
+			return nil, status.Error(codes.InvalidArgument, "expression.range should not be null")
+		}
 	}
 	if req.Option == nil {
 		return nil, status.Error(codes.InvalidArgument, "option should not be null")
 	}
 
-	expr, diags := hclext.ParseExpression(req.Expr, req.ExprRange.Filename, fromproto.Pos(req.ExprRange.Start))
+	var expr hcl.Expression
+	var diags hcl.Diagnostics
+	if req.Expression != nil {
+		expr, diags = fromproto.Expression(req.Expression)
+	} else {
+		expr, diags = hclext.ParseExpression(req.Expr, req.ExprRange.Filename, fromproto.Pos(req.ExprRange.Start))
+	}
 	if diags.HasErrors() {
 		return nil, toproto.Error(codes.InvalidArgument, diags)
 	}