Update markdown parsing library to github.com/gomarkdown/markdown (#944)

vendor/github.com/gomarkdown/markdown/parser/attribute.go

@@ -0,0 +1,116 @@
+package parser
+
+import (
+	"bytes"
+
+	"github.com/gomarkdown/markdown/ast"
+)
+
+// attribute parses a (potential) block attribute and adds it to p.
+func (p *Parser) attribute(data []byte) []byte {
+	if len(data) < 3 {
+		return data
+	}
+	i := 0
+	if data[i] != '{' {
+		return data
+	}
+	i++
+
+	// last character must be a } otherwise it's not an attribute
+	end := skipUntilChar(data, i, '\n')
+	if data[end-1] != '}' {
+		return data
+	}
+
+	i = skipSpace(data, i)
+	b := &ast.Attribute{Attrs: make(map[string][]byte)}
+
+	esc := false
+	quote := false
+	trail := 0
+Loop:
+	for ; i < len(data); i++ {
+		switch data[i] {
+		case ' ', '\t', '\f', '\v':
+			if quote {
+				continue
+			}
+			chunk := data[trail+1 : i]
+			if len(chunk) == 0 {
+				trail = i
+				continue
+			}
+			switch {
+			case chunk[0] == '.':
+				b.Classes = append(b.Classes, chunk[1:])
+			case chunk[0] == '#':
+				b.ID = chunk[1:]
+			default:
+				k, v := keyValue(chunk)
+				if k != nil && v != nil {
+					b.Attrs[string(k)] = v
+				} else {
+					// this is illegal in an attribute
+					return data
+				}
+			}
+			trail = i
+		case '"':
+			if esc {
+				esc = !esc
+				continue
+			}
+			quote = !quote
+		case '\\':
+			esc = !esc
+		case '}':
+			if esc {
+				esc = !esc
+				continue
+			}
+			chunk := data[trail+1 : i]
+			if len(chunk) == 0 {
+				return data
+			}
+			switch {
+			case chunk[0] == '.':
+				b.Classes = append(b.Classes, chunk[1:])
+			case chunk[0] == '#':
+				b.ID = chunk[1:]
+			default:
+				k, v := keyValue(chunk)
+				if k != nil && v != nil {
+					b.Attrs[string(k)] = v
+				} else {
+					return data
+				}
+			}
+			i++
+			break Loop
+		default:
+			esc = false
+		}
+	}
+
+	p.attr = b
+	return data[i:]
+}
+
+// key="value" quotes are mandatory.
+func keyValue(data []byte) ([]byte, []byte) {
+	chunk := bytes.SplitN(data, []byte{'='}, 2)
+	if len(chunk) != 2 {
+		return nil, nil
+	}
+	key := chunk[0]
+	value := chunk[1]
+
+	if len(value) < 3 || len(key) == 0 {
+		return nil, nil
+	}
+	if value[0] != '"' || value[len(value)-1] != '"' {
+		return key, nil
+	}
+	return key, value[1 : len(value)-1]
+}