fix(loader): do not drop values files ending at a 4096-byte boundary

YAMLReader can return EOF without yielding the last line when that line
has no trailing newline and its length is a multiple of bufio's default
buffer. Read the file fully and ensure a trailing newline before parsing
so compact JSON values files are not silently ignored.

Fixes #32506

Signed-off-by: Dean Chen <862469039@qq.com>

internal/chart/v3/loader/load.go

@@ -183,8 +183,20 @@ func LoadFiles(files []*archive.BufferedFile) (*chart.Chart, error) {
 // The reader is expected to contain one or more YAML documents, the values of which are merged.
 // And the values can be either a chart's default values or user-supplied values.
 func LoadValues(data io.Reader) (map[string]any, error) {
+	// Read fully first. YAMLReader/LineReader can drop a final unterminated
+	// line when its length is an exact multiple of bufio.Reader's default
+	// buffer (4096). Appending a trailing newline avoids that case.
+	// See https://github.com/helm/helm/issues/32506
+	b, err := io.ReadAll(data)
+	if err != nil {
+		return nil, err
+	}
+	if len(b) > 0 && b[len(b)-1] != '\n' {
+		b = append(b, '\n')
+	}
+
 	values := map[string]any{}
-	reader := utilyaml.NewYAMLReader(bufio.NewReader(data))
+	reader := utilyaml.NewYAMLReader(bufio.NewReader(bytes.NewReader(b)))
 	for {
 		currentMap := map[string]any{}
 		raw, err := reader.Read()

internal/chart/v3/loader/load_test.go

@@ -419,6 +419,29 @@ foo:
 	}
 }
 
+
+func TestLoadValuesEOFBoundary(t *testing.T) {
+	// Reproduces #32506: a single logical line whose length is a multiple of
+	// bufio's default buffer (4096) and has no trailing newline used to be
+	// dropped entirely by YAMLReader, yielding empty values.
+	prefix := []byte(`{"foo":"`)
+	suffix := []byte(`"}`)
+	pad := 4096 - len(prefix) - len(suffix)
+	data := make([]byte, 0, 4096)
+	data = append(data, prefix...)
+	data = append(data, bytes.Repeat([]byte("x"), pad)...)
+	data = append(data, suffix...)
+	if len(data) != 4096 {
+		t.Fatalf("test setup: want data length 4096, got %d", len(data))
+	}
+
+	values, err := LoadValues(bytes.NewReader(data))
+	require.NoError(t, err)
+	assert.Equal(t, map[string]any{
+		"foo": string(bytes.Repeat([]byte("x"), pad)),
+	}, values)
+}
+
 func TestMergeValuesV3(t *testing.T) {
 	nestedMap := map[string]any{
 		"foo": "bar",

pkg/chart/v2/loader/load.go

@@ -210,8 +210,20 @@ func LoadFiles(files []*archive.BufferedFile) (*chart.Chart, error) {
 // The reader is expected to contain one or more YAML documents, the values of which are merged.
 // And the values can be either a chart's default values or user-supplied values.
 func LoadValues(data io.Reader) (map[string]any, error) {
+	// Read fully first. YAMLReader/LineReader can drop a final unterminated
+	// line when its length is an exact multiple of bufio.Reader's default
+	// buffer (4096). Appending a trailing newline avoids that case.
+	// See https://github.com/helm/helm/issues/32506
+	b, err := io.ReadAll(data)
+	if err != nil {
+		return nil, err
+	}
+	if len(b) > 0 && b[len(b)-1] != '\n' {
+		b = append(b, '\n')
+	}
+
 	values := map[string]any{}
-	reader := utilyaml.NewYAMLReader(bufio.NewReader(data))
+	reader := utilyaml.NewYAMLReader(bufio.NewReader(bytes.NewReader(b)))
 	for {
 		currentMap := map[string]any{}
 		raw, err := reader.Read()

pkg/chart/v2/loader/load_test.go

@@ -463,6 +463,29 @@ foo:
 	}
 }
 
+
+func TestLoadValuesEOFBoundary(t *testing.T) {
+	// Reproduces #32506: a single logical line whose length is a multiple of
+	// bufio's default buffer (4096) and has no trailing newline used to be
+	// dropped entirely by YAMLReader, yielding empty values.
+	prefix := []byte(`{"foo":"`)
+	suffix := []byte(`"}`)
+	pad := 4096 - len(prefix) - len(suffix)
+	data := make([]byte, 0, 4096)
+	data = append(data, prefix...)
+	data = append(data, bytes.Repeat([]byte("x"), pad)...)
+	data = append(data, suffix...)
+	if len(data) != 4096 {
+		t.Fatalf("test setup: want data length 4096, got %d", len(data))
+	}
+
+	values, err := LoadValues(bytes.NewReader(data))
+	require.NoError(t, err)
+	assert.Equal(t, map[string]any{
+		"foo": string(bytes.Repeat([]byte("x"), pad)),
+	}, values)
+}
+
 func TestMergeValuesV2(t *testing.T) {
 	nestedMap := map[string]any{
 		"foo": "bar",