bake: format hcl errors with source definition

Signed-off-by: Tonis Tiigi <tonistiigi@gmail.com>

bake/hcl.go

@@ -9,6 +9,8 @@ import (
 	"github.com/hashicorp/hcl/v2/hclsimple"
 	"github.com/hashicorp/hcl/v2/hclsyntax"
 	"github.com/hashicorp/hcl/v2/json"
+	"github.com/moby/buildkit/solver/errdefs"
+	"github.com/moby/buildkit/solver/pb"
 	"github.com/zclconf/go-cty/cty"
 	"github.com/zclconf/go-cty/cty/function"
 	"github.com/zclconf/go-cty/cty/function/stdlib"
@@ -103,7 +105,11 @@ type staticConfig struct {
 	Remain    hcl.Body    `hcl:",remain"`
 }
 
-func ParseHCL(dt []byte, fn string) (*Config, error) {
+func ParseHCL(dt []byte, fn string) (_ *Config, err error) {
+	defer func() {
+		err = formatHCLError(dt, err)
+	}()
+
 	// Decode user defined functions, first parsing as hcl and falling back to
 	// json, returning errors based on the file suffix.
 	file, hcldiags := hclsyntax.ParseConfig(dt, fn, hcl.Pos{Line: 1, Column: 1})
@@ -172,3 +178,35 @@ func ParseHCL(dt []byte, fn string) (*Config, error) {
 	}
 	return &c, nil
 }
+
+func formatHCLError(dt []byte, err error) error {
+	if err == nil {
+		return nil
+	}
+	diags, ok := err.(hcl.Diagnostics)
+	if !ok {
+		return err
+	}
+	for _, d := range diags {
+		if d.Severity != hcl.DiagError {
+			continue
+		}
+		src := errdefs.Source{
+			Info: &pb.SourceInfo{
+				Filename: d.Subject.Filename,
+				Data:     dt,
+			},
+			Ranges: []*pb.Range{toErrRange(d.Subject)},
+		}
+		err = errdefs.WithSource(err, src)
+		break
+	}
+	return err
+}
+
+func toErrRange(in *hcl.Range) *pb.Range {
+	return &pb.Range{
+		Start: pb.Position{Line: int32(in.Start.Line), Character: int32(in.Start.Column)},
+		End:   pb.Position{Line: int32(in.End.Line), Character: int32(in.End.Column)},
+	}
+}