Resolves a false-positive detection of multi-doc YAML streams (#693)

Fixes #673.

builtins.go

@@ -1406,8 +1406,6 @@ func builtinParseYAML(i *interpreter, str value) (value, error) {
 	}
 	s := sval.getGoString()
 
-	isYamlStream := strings.Contains(s, "---")
-
 	elems := []interface{}{}
 	d := NewYAMLToJSONDecoder(strings.NewReader(s))
 	for {
@@ -1421,7 +1419,7 @@ func builtinParseYAML(i *interpreter, str value) (value, error) {
 		elems = append(elems, elem)
 	}
 
-	if isYamlStream {
+	if d.IsStream() {
 		return jsonToValue(i, elems)
 	}
 	return jsonToValue(i, elems[0])

testdata/parseYaml.golden

@@ -1,10 +1,41 @@
-{
-   "aaa": { },
-   "foo": "bar",
-   "xxx": [
-      42,
-      "asdf",
-      { }
+[
+   {
+      "aaa": { },
+      "foo": "bar",
+      "xxx": [
+         42,
+         "asdf",
+         { }
+      ],
+      "ąę": "ćż"
+   },
+   [
+      {
+         "a": 1
+      },
+      {
+         "a": 2
+      }
    ],
-   "ąę": "ćż"
-}
+   [
+      {
+         "a": 1
+      },
+      {
+         "a": 2
+      }
+   ],
+   [
+      {
+         "a": 1
+      },
+      {
+         "a": 2
+      }
+   ],
+   {
+      "---a": 2,
+      "a": 1,
+      "a---": 3
+   }
+]

testdata/parseYaml.jsonnet

@@ -1,11 +1,46 @@
-std.parseYaml(
-  |||
-   foo: bar
-   aaa: {}
-   ąę: ćż
-   xxx:
-   - 42
-   - asdf
-   - {}
-  |||
-)
+[
+  std.parseYaml(text)
+  for text in [
+    // various node types
+    |||
+      foo: bar
+      aaa: {}
+      ąę: ćż
+      xxx:
+      - 42
+      - asdf
+      - {}
+    |||,
+
+    // Returns an array of documents when there is an explicit document(s), i.e.
+    // the text is a "multi-doc" stream
+    |||
+      ---
+      a: 1
+      ---
+      a: 2
+    |||,
+
+    // The first document in a "multi-doc" stream can be an implicit document.
+    |||
+      a: 1
+      ---
+      a: 2
+    |||,
+
+    // Whitespaces are allowed after the document start marker
+    |||
+      ---
+      a: 1
+      ---   
+      a: 2
+    |||,
+
+    // Document start marker needs a following line break or a whitespace.
+    |||
+      a: 1
+      ---a: 2
+      a---: 3
+    |||,
+  ]
+]

yaml.go

@@ -32,7 +32,7 @@ const separator = "---"
 // separating individual documents. It first converts the YAML
 // body to JSON, then unmarshals the JSON.
 type YAMLToJSONDecoder struct {
-	reader Reader
+	reader *YAMLReader
 }
 
 // NewYAMLToJSONDecoder decodes YAML documents from the provided
@@ -50,7 +50,7 @@ func NewYAMLToJSONDecoder(r io.Reader) *YAMLToJSONDecoder {
 // an error. The decoding rules match json.Unmarshal, not
 // yaml.Unmarshal.
 func (d *YAMLToJSONDecoder) Decode(into interface{}) error {
-	bytes, err := d.reader.Read()
+	bytes, err := d.reader.read()
 	if err != nil && err != io.EOF {
 		return err
 	}
@@ -64,6 +64,10 @@ func (d *YAMLToJSONDecoder) Decode(into interface{}) error {
 	return err
 }
 
+func (d *YAMLToJSONDecoder) IsStream() bool {
+	return d.reader.isStream()
+}
+
 // Reader reads bytes
 type Reader interface {
 	Read() ([]byte, error)
@@ -72,6 +76,7 @@ type Reader interface {
 // YAMLReader reads YAML
 type YAMLReader struct {
 	reader Reader
+	stream bool
 }
 
 // NewYAMLReader creates a new YAMLReader
@@ -82,7 +87,7 @@ func NewYAMLReader(r *bufio.Reader) *YAMLReader {
 }
 
 // Read returns a full YAML document.
-func (r *YAMLReader) Read() ([]byte, error) {
+func (r *YAMLReader) read() ([]byte, error) {
 	var buffer bytes.Buffer
 	for {
 		line, err := r.reader.Read()
@@ -96,6 +101,7 @@ func (r *YAMLReader) Read() ([]byte, error) {
 			i += sep
 			after := line[i:]
 			if len(strings.TrimRightFunc(string(after), unicode.IsSpace)) == 0 {
+				r.stream = true
 				if buffer.Len() != 0 {
 					return buffer.Bytes(), nil
 				}
@@ -115,6 +121,10 @@ func (r *YAMLReader) Read() ([]byte, error) {
 	}
 }
 
+func (r *YAMLReader) isStream() bool {
+	return r.stream
+}
+
 // LineReader reads single lines.
 type LineReader struct {
 	reader *bufio.Reader