Merge pull request #487 from twobiers/error-print-line

Add error context to YAML errors for better debugging

Author: bobh66

fn.go

@@ -4,9 +4,11 @@ import (
 	"bytes"
 	"context"
 	"encoding/base64"
+	"fmt"
 	"io"
 	"io/fs"
 	"os"
+	"strings"
 	"text/template"
 
 	"dario.cat/mergo"
@@ -45,6 +47,13 @@ type Function struct {
 	fsys fs.FS
 }
 
+type YamlErrorContext struct {
+	RelLine int
+	AbsLine int
+	Message string
+	Context string
+}
+
 const (
 	annotationKeyCompositionResourceName = "gotemplating.fn.crossplane.io/composition-resource-name"
 	annotationKeyReady                   = "gotemplating.fn.crossplane.io/ready"
@@ -106,14 +115,34 @@ func (f *Function) RunFunction(_ context.Context, req *fnv1.RunFunctionRequest)
 
 	// Parse the rendered manifests.
 	var objs []*unstructured.Unstructured
-	decoder := yaml.NewYAMLOrJSONDecoder(bytes.NewBufferString(buf.String()), 1024)
+	data := buf.String()
+	decoder := yaml.NewYAMLOrJSONDecoder(bytes.NewBufferString(data), 1024)
+
+	lines := strings.Split(data, "\n")
+	startLine := moveToNextDoc(lines, 1)
+	docIndex := 0
+
 	for {
 		u := &unstructured.Unstructured{}
 		if err := decoder.Decode(&u); err != nil {
 			if err == io.EOF {
 				break
 			}
-			response.Fatal(rsp, errors.Wrap(err, "cannot decode manifest"))
+
+			var newErr error
+			yamlErr := getYamlErrorContextFromErr(err, startLine, lines)
+			if yamlErr == (YamlErrorContext{}) {
+				newErr = err
+			} else {
+				context := strings.TrimSpace(yamlErr.Context)
+				if len(context) > 80 {
+					context = context[:80] + "..."
+				}
+
+				newErr = fmt.Errorf("error converting YAML to JSON: yaml: line %d (document %d, line %d) near: '%s': %s", yamlErr.AbsLine, docIndex+1, yamlErr.RelLine, context, yamlErr.Message)
+			}
+
+			response.Fatal(rsp, errors.Wrap(newErr, "cannot decode manifest"))
 			return rsp, nil
 		}
 
@@ -131,6 +160,9 @@ func (f *Function) RunFunction(_ context.Context, req *fnv1.RunFunctionRequest)
 		}
 
 		objs = append(objs, u)
+
+		startLine = moveToNextDoc(lines, startLine)
+		docIndex++
 	}
 
 	// Get the desired composite resource from the request.
@@ -328,3 +360,38 @@ func safeApplyTemplateOptions(templ *template.Template, options []string) (err e
 	templ.Option(options...)
 	return nil
 }
+
+func moveToNextDoc(lines []string, startLine int) int {
+	for i := startLine; i <= len(lines); i++ {
+		if strings.TrimSpace(lines[i-1]) == "---" && i > startLine {
+			return i
+		}
+	}
+	return startLine
+}
+
+func getYamlErrorContextFromErr(err error, startLine int, lines []string) YamlErrorContext {
+	var relLine int
+	n, scanErr := fmt.Sscanf(err.Error(), "error converting YAML to JSON: yaml: line %d:", &relLine)
+	var errMsg string
+	if scanErr == nil && n == 1 {
+		// Extract the rest of the error message after the matched prefix.
+		prefix := fmt.Sprintf("error converting YAML to JSON: yaml: line %d:", relLine)
+		errStr := err.Error()
+		if idx := strings.Index(errStr, prefix); idx != -1 {
+			errMsg = strings.TrimSpace(errStr[idx+len(prefix):])
+		}
+	}
+	if scanErr == nil && n == 1 {
+		absLine := startLine + relLine
+		if absLine-1 < len(lines) && absLine-1 >= 0 {
+			return YamlErrorContext{
+				RelLine: relLine,
+				AbsLine: absLine,
+				Message: errMsg,
+				Context: lines[absLine-1],
+			}
+		}
+	}
+	return YamlErrorContext{}
+}

fn_test.go

@@ -22,6 +22,14 @@ import (
 )
 
 var (
+	invalidYaml = `
+---
+apiVersion: example.org/v1
+kind: CD
+metadata:
+  name: %!@#$%^&*()_+
+`
+
 	cd                    = `{"apiVersion":"example.org/v1","kind":"CD","metadata":{"annotations":{"gotemplating.fn.crossplane.io/composition-resource-name":"cool-cd"},"name":"cool-cd"}}`
 	cdTmpl                = `{"apiVersion":"example.org/v1","kind":"CD","metadata":{"annotations":{"gotemplating.fn.crossplane.io/composition-resource-name":"cool-cd"},"name":"cool-cd","labels":{"belongsTo":{{.observed.composite.resource.metadata.name|quote}}}}}`
 	cdMissingKeyTmpl      = `{"apiVersion":"example.org/v1","kind":"CD","metadata":{"name":"cool-cd","labels":{"belongsTo":{{.missing | quote }}}}}`
@@ -1191,6 +1199,45 @@ func TestRunFunction(t *testing.T) {
 				},
 			},
 		},
+		"PrintYamlErrorLine": {
+			reason: "The Function should print the line content when invalid YAML is provided.",
+			args: args{
+				req: &fnv1.RunFunctionRequest{
+					Input: resource.MustStructObject(
+						&v1beta1.GoTemplate{
+							Source: v1beta1.InlineSource,
+							Inline: &v1beta1.TemplateSourceInline{Template: invalidYaml},
+						}),
+					Observed: &fnv1.State{
+						Composite: &fnv1.Resource{
+							Resource: resource.MustStructJSON(xr),
+						},
+					},
+					Desired: &fnv1.State{
+						Composite: &fnv1.Resource{
+							Resource: resource.MustStructJSON(xr),
+						},
+					},
+				},
+			},
+			want: want{
+				rsp: &fnv1.RunFunctionResponse{
+					Meta: &fnv1.ResponseMeta{Ttl: durationpb.New(response.DefaultTTL)},
+					Results: []*fnv1.Result{
+						{
+							Severity: fnv1.Severity_SEVERITY_FATAL,
+							Message:  "cannot decode manifest: error converting YAML to JSON: yaml: line 6 (document 1, line 4) near: 'name: %!@#$%^&*()_+': found character that cannot start any token",
+							Target:   fnv1.Target_TARGET_COMPOSITE.Enum(),
+						},
+					},
+					Desired: &fnv1.State{
+						Composite: &fnv1.Resource{
+							Resource: resource.MustStructJSON(xr),
+						},
+					},
+				},
+			},
+		},
 	}
 
 	for name, tc := range cases {