CLI: display error details for ErrorDetail errors in eval output

internal/presentation/presentation.go

@@ -198,8 +198,9 @@ func NewOutputErrors(err error) []OutputError {
 				Message: err.Error(),
 				err:     typedErr,
 			}}
-			if d, ok := err.(rego.ErrorWithDetails); ok {
-				errs[0].Details = d.Details()
+			if d, ok := err.(rego.ErrorDetails); ok {
+				details := strings.Join(d.Lines(), "\n")
+				errs[0].Details = details
 			}
 		}
 	}
@@ -215,16 +216,22 @@ func (e OutputErrors) Error() string {
 		return "no error(s)"
 	}
 
+	var prefix string
 	if len(e) == 1 {
-		return fmt.Sprintf("1 error occurred: %v", e[0].Error())
+		prefix = "1 error occurred: "
+	} else {
+		prefix = fmt.Sprintf("%d errors occurred:\n", len(e))
 	}
 
 	var s []string
 	for _, err := range e {
 		s = append(s, err.Error())
+		if l, ok := err.Details.(string); ok {
+			s = append(s, l)
+		}
 	}
 
-	return fmt.Sprintf("%d errors occurred:\n%s", len(e), strings.Join(s, "\n"))
+	return prefix + strings.Join(s, "\n")
 }
 
 // OutputError provides a common structure for all OPA

internal/presentation/presentation_test.go

@@ -38,12 +38,8 @@ func (t *testErrorWithMarshaller) MarshalJSON() ([]byte, error) {
 
 type testErrorWithDetails struct{}
 
-func (*testErrorWithDetails) Error() string { return "something went wrong" }
-func (*testErrorWithDetails) Details() string {
-	return `oh
-so
-wrong`
-}
+func (*testErrorWithDetails) Error() string   { return "something went wrong" }
+func (*testErrorWithDetails) Lines() []string { return []string{"oh", "so", "wrong"} }
 
 func validateJSONOutput(t *testing.T, testErr error, expected string) {
 	t.Helper()
@@ -487,7 +483,7 @@ func TestRaw(t *testing.T) {
 			output: Output{
 				Errors: NewOutputErrors(&testErrorWithDetails{}),
 			},
-			want: "1 error occurred: something went wrong\n",
+			want: "1 error occurred: something went wrong\noh\nso\nwrong\n",
 		},
 	}
 

internal/rego/opa/engine.go

@@ -15,14 +15,15 @@ var ErrEngineNotFound error = &errEngineNotFound{}
 type errEngineNotFound struct{}
 
 func (*errEngineNotFound) Error() string { return "engine not found" }
-func (*errEngineNotFound) Details() string {
-	return `WebAssembly runtime not supported in this build.
-----------------------------------------------------------------------------------
-Please download an OPA binary with Wasm enabled from
-https://www.openpolicyagent.org/docs/latest/#running-opa
-or build it yourself (with Wasm enabled).
-----------------------------------------------------------------------------------
-`
+func (*errEngineNotFound) Lines() []string {
+	return []string{
+		`WebAssembly runtime not supported in this build.`,
+		`----------------------------------------------------------------------------------`,
+		`Please download an OPA binary with Wasm enabled from`,
+		`https://www.openpolicyagent.org/docs/latest/#running-opa`,
+		`or build it yourself (with Wasm enabled).`,
+		`----------------------------------------------------------------------------------`,
+	}
 }
 
 // Engine repesents a factory for instances of EvalEngine implementations

rego/errors.go

@@ -17,8 +17,8 @@ func NewHaltError(err error) error {
 	return &HaltError{err: err}
 }
 
-// ErrorWithDetails interface is satisfied by an error that provides further
+// ErrorDetails interface is satisfied by an error that provides further
 // details.
-type ErrorWithDetails interface {
-	Details() string
+type ErrorDetails interface {
+	Lines() []string
 }