fix: skip empty documents on config decoding

internal/app/machined/pkg/controllers/config/acquire_test.go

@@ -349,10 +349,15 @@ func (suite *AcquireSuite) TestFromDiskFailure() {
 	ev := suite.platformEvent.getEvents()[0]
 	suite.Assert().Equal(platform.EventTypeFailure, ev.Type)
 	suite.Assert().Equal("Error loading and validating Talos machine config.", ev.Message)
-	suite.Assert().Equal("failed to load \"config.yaml\" from STATE: unknown keys found during decoding:\naaaversion: v1alpha1 # Indicates the schema used to decode the contents.\n", ev.Error.Error())
+	suite.Assert().Equal(
+		"failed to load \"config.yaml\" from STATE: error decoding document /v1alpha1/ (line 1): unknown keys found during decoding:\n"+
+			"aaaversion: v1alpha1 # Indicates the schema used to decode the contents.\n",
+		ev.Error.Error(),
+	)
 
 	suite.Assert().Equal(&machineapi.ConfigLoadErrorEvent{
-		Error: "failed to load \"config.yaml\" from STATE: unknown keys found during decoding:\naaaversion: v1alpha1 # Indicates the schema used to decode the contents.\n",
+		Error: "failed to load \"config.yaml\" from STATE: error decoding document /v1alpha1/ (line 1): unknown keys found during decoding:\n" +
+			"aaaversion: v1alpha1 # Indicates the schema used to decode the contents.\n",
 	}, suite.eventPublisher.getEvents()[0])
 }
 

pkg/machinery/config/configloader/internal/decoder/decoder.go

@@ -85,13 +85,13 @@ func parse(r io.Reader, allowPatchDelete bool) (decoded []config.Document, err e
 		}
 
 		if manifests.Kind != yaml.DocumentNode {
-			return nil, errors.New("expected a document")
+			return nil, fmt.Errorf("expected a document at line %d", manifests.Line)
 		}
 
 		if allowPatchDelete {
 			decoded, err = AppendDeletesTo(&manifests, decoded, i)
 			if err != nil {
-				return nil, err
+				return nil, fmt.Errorf("error processing patch delete statements at line %d: %w", manifests.Line, err)
 			}
 
 			if manifests.IsZero() {
@@ -100,22 +100,36 @@ func parse(r io.Reader, allowPatchDelete bool) (decoded []config.Document, err e
 		}
 
 		for _, manifest := range manifests.Content {
+			switch manifest.Kind { //nolint:exhaustive
+			case yaml.MappingNode:
+				// expected
+			case yaml.ScalarNode:
+				if manifest.Tag == "!!null" {
+					// skip null documents
+					continue
+				}
+
+				fallthrough
+			default:
+				return nil, fmt.Errorf("expected a YAML document at line %d", manifest.Line)
+			}
+
 			id := documentID{
 				APIVersion: findValue(manifest, ManifestAPIVersionKey, false),
 				Kind:       cmp.Or(findValue(manifest, ManifestKindKey, false), "v1alpha1"),
 				Name:       findValue(manifest, "name", false),
 			}
 
 			if _, ok := knownDocuments[id]; ok {
-				return nil, fmt.Errorf("duplicate document %s/%s/%s is not allowed", id.APIVersion, id.Kind, id.Name)
+				return nil, fmt.Errorf("duplicate document %s/%s/%s is not allowed (line %d)", id.APIVersion, id.Kind, id.Name, manifest.Line)
 			}
 
 			knownDocuments[id] = struct{}{}
 
 			var target config.Document
 
 			if target, err = decode(manifest); err != nil {
-				return nil, err
+				return nil, fmt.Errorf("error decoding document %s/%s/%s (line %d): %w", id.APIVersion, id.Kind, id.Name, manifest.Line, err)
 			}
 
 			decoded = append(decoded, target)

pkg/machinery/config/configloader/internal/decoder/decoder_test.go

@@ -120,6 +120,22 @@ func TestDecoder(t *testing.T) {
 kind: mock
 apiVersion: v1alpha1
 test: true
+`),
+			expected: []config.Document{
+				&Mock{
+					Test: true,
+				},
+			},
+			expectedErr: "",
+		},
+		{
+			name: "empty docs",
+			source: []byte(`---
+kind: mock
+apiVersion: v1alpha1
+test: true
+---
+---
 `),
 			expected: []config.Document{
 				&Mock{
@@ -135,7 +151,7 @@ apiVersion: v1alpha2
 test: true
 `),
 			expected:    nil,
-			expectedErr: "missing kind",
+			expectedErr: "error decoding document v1alpha2/v1alpha1/ (line 2): missing kind",
 		},
 		{
 			name: "empty kind",
@@ -145,7 +161,7 @@ apiVersion: v1alpha2
 test: true
 `),
 			expected:    nil,
-			expectedErr: "missing kind",
+			expectedErr: "error decoding document v1alpha2/v1alpha1/ (line 2): missing kind",
 		},
 		{
 			name: "tab instead of spaces",
@@ -167,7 +183,7 @@ test: true
 extra: fail
 `),
 			expected:    nil,
-			expectedErr: "unknown keys found during decoding:\nextra: fail\n",
+			expectedErr: "error decoding document v1alpha1/mock/ (line 2): unknown keys found during decoding:\nextra: fail\n",
 		},
 		{
 			name: "extra fields in map",
@@ -180,7 +196,7 @@ map:
     extra: me
 `),
 			expected:    nil,
-			expectedErr: "unknown keys found during decoding:\nmap:\n    first:\n        extra: me\n",
+			expectedErr: "error decoding document v1alpha2/mock/ (line 2): unknown keys found during decoding:\nmap:\n    first:\n        extra: me\n",
 		},
 		{
 			name: "extra fields in slice",
@@ -194,7 +210,7 @@ slice:
     fields: here
 `),
 			expected:    nil,
-			expectedErr: "unknown keys found during decoding:\nslice:\n    - fields: here\n      more: extra\n      not: working\n",
+			expectedErr: "error decoding document v1alpha2/mock/ (line 2): unknown keys found during decoding:\nslice:\n    - fields: here\n      more: extra\n      not: working\n",
 		},
 		{
 			name: "extra zero fields in map",
@@ -207,7 +223,7 @@ map:
       b: {}
 `),
 			expected:    nil,
-			expectedErr: "unknown keys found during decoding:\nmap:\n    second:\n        a:\n            b: {}\n",
+			expectedErr: "error decoding document v1alpha2/mock/ (line 2): unknown keys found during decoding:\nmap:\n    second:\n        a:\n            b: {}\n",
 		},
 		{
 			name: "valid nested",
@@ -306,7 +322,7 @@ config:
           - content: MONITOR ${upsmonHost} 1 remote pass foo
             mountPath: /usr/local/etc/nut/upsmon.conf
 `),
-			expectedErr: "\"ExtensionServiceConfig\" \"\": not registered",
+			expectedErr: "error decoding document /ExtensionServiceConfig/ (line 2): \"ExtensionServiceConfig\" \"\": not registered",
 		},
 	}