Report assembly error strings for compile API endpoint (#3190)

* Add error strings to v2 TEAL compile endpoint

* Move number of errors to end so it is consistent with goal clerk compile

* Refactor ReportProblems() to take io.Writer

* Don't report number of errors on the API call

Author: algochoi

cmd/goal/clerk.go

@@ -922,7 +922,7 @@ func assembleFile(fname string) (program []byte) {
 	}
 	ops, err := logic.AssembleString(string(text))
 	if err != nil {
-		ops.ReportProblems(fname)
+		ops.ReportProblems(fname, os.Stderr)
 		reportErrorf("%s: %s", fname, err)
 	}
 	_, params := getProto(protoVersion)

cmd/goal/multisig.go

@@ -20,6 +20,7 @@ import (
 	"fmt"
 	"io"
 	"io/ioutil"
+	"os"
 
 	"github.com/spf13/cobra"
 
@@ -163,7 +164,7 @@ var signProgramCmd = &cobra.Command{
 			}
 			ops, err := logic.AssembleString(string(text))
 			if err != nil {
-				ops.ReportProblems(programSource)
+				ops.ReportProblems(programSource, os.Stderr)
 				reportErrorf("%s: %s", programSource, err)
 			}
 			if outname == "" {

cmd/pingpong/runCmd.go

@@ -242,7 +242,7 @@ var runCmd = &cobra.Command{
 			}
 			ops, err := logic.AssembleString(programStr)
 			if err != nil {
-				ops.ReportProblems(teal)
+				ops.ReportProblems(teal, os.Stderr)
 				reportErrorf("Internal error, cannot assemble %v \n", programStr)
 			}
 			cfg.Program = ops.Program

daemon/algod/api/server/v2/handlers.go

@@ -24,6 +24,7 @@ import (
 	"io"
 	"math"
 	"net/http"
+	"strings"
 	"time"
 
 	"github.com/labstack/echo/v4"
@@ -754,7 +755,9 @@ func (v2 *Handlers) TealCompile(ctx echo.Context) error {
 	source := buf.String()
 	ops, err := logic.AssembleString(source)
 	if err != nil {
-		return badRequest(ctx, err, err.Error(), v2.Log)
+		sb := strings.Builder{}
+		ops.ReportProblems("", &sb)
+		return badRequest(ctx, err, sb.String(), v2.Log)
 	}
 	pd := logic.HashProgram(ops.Program)
 	addr := basics.Address(pd)

data/transactions/logic/assembler.go

@@ -27,7 +27,6 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"os"
 	"sort"
 	"strconv"
 	"strings"
@@ -2109,19 +2108,27 @@ func (ops *OpStream) warnf(format string, a ...interface{}) error {
 	return ops.warn(fmt.Errorf(format, a...))
 }
 
-// ReportProblems issues accumulated warnings and errors to stderr.
-func (ops *OpStream) ReportProblems(fname string) {
+// ReportProblems issues accumulated warnings and outputs errors to an io.Writer.
+func (ops *OpStream) ReportProblems(fname string, writer io.Writer) {
 	for i, e := range ops.Errors {
 		if i > 9 {
 			break
 		}
-		fmt.Fprintf(os.Stderr, "%s: %s\n", fname, e)
+		if fname == "" {
+			fmt.Fprintf(writer, "%s\n", e)
+		} else {
+			fmt.Fprintf(writer, "%s: %s\n", fname, e)
+		}
 	}
 	for i, w := range ops.Warnings {
 		if i > 9 {
 			break
 		}
-		fmt.Fprintf(os.Stderr, "%s: %s\n", fname, w)
+		if fname == "" {
+			fmt.Fprintf(writer, "%s\n", w)
+		} else {
+			fmt.Fprintf(writer, "%s: %s\n", fname, w)
+		}
 	}
 }