draft add info identifiers in the comments

Author: Ying WANG

model/textparse/README.md

@@ -3,4 +3,4 @@ In the rare case that you need to update the textparse lexers, edit promlex.l or
 `golex -o=promlex.l.go promlex.l`
 
 Note that you need golex installed: 
-`go get -u modernc.org/golex`
+`go install -u modernc.org/golex@latest`

model/textparse/interface.go

@@ -51,6 +51,9 @@ type Parser interface {
 	// The returned byte slices become invalid after the next call to Next.
 	Unit() ([]byte, []byte)
 
+	// Identifiers returns the identifiers for info metrics
+	Identifiers() []string
+
 	// Comment returns the text of the current comment.
 	// Must only be called after Next returned a comment entry.
 	// The returned byte slice becomes invalid after the next call to Next.
@@ -110,4 +113,5 @@ const (
 	EntryComment   Entry = 3
 	EntryUnit      Entry = 4
 	EntryHistogram Entry = 5 // A series with a native histogram as a value.
+	EntryIdent     Entry = 6
 )

model/textparse/openmetricslex.l

@@ -36,7 +36,7 @@ M     [a-zA-Z_:]
 C     [^\n]
 S     [ ]
 
-%x sComment sMeta1 sMeta2 sLabels sLValue sValue sTimestamp sExemplar sEValue sETimestamp
+%x sComment sMeta1 sMeta2 sLabels sLValue sValue sTimestamp sExemplar sEValue sETimestamp sMeta3
 
 %yyc c
 %yyn c = l.next()
@@ -50,9 +50,13 @@ S     [ ]
 <sComment>TYPE{S}                     l.state = sMeta1; return tType
 <sComment>UNIT{S}                     l.state = sMeta1; return tUnit
 <sComment>"EOF"\n?                    l.state = sInit; return tEOFWord
+<sComment>IDENS{S}                    l.state = sMeta3; return tIdens
 <sMeta1>\"(\\.|[^\\"])*\"             l.state = sMeta2; return tMName
 <sMeta1>{M}({M}|{D})*                 l.state = sMeta2; return tMName
 <sMeta2>{S}{C}*\n                     l.state = sInit; return tText
+<sMeta3>{L}*                          return tLName
+<sMeta3>,                             return tComma
+<sMeta3>\n                            l.state = sInit; return tLinebreak
 
 {M}({M}|{D})*                         l.state = sValue; return tMName
 <sValue>\{                            l.state = sLabels; return tBraceOpen