Adds Inf and NaN as Numbers to Histogram in Promql Testing Framework (#13916)

includes Inf and NaN as numbers to histogram

---------

Signed-off-by: Neeraj Gartia <neerajgartia211002@gmail.com>
Signed-off-by: Björn Rabenstein <github@rabenste.in>
Co-authored-by: Björn Rabenstein <github@rabenste.in>

promql/parser/lex.go

@@ -519,7 +519,7 @@ func lexHistogram(l *Lexer) stateFn {
 		return lexHistogram
 	case r == '-':
 		l.emit(SUB)
-		return lexNumber
+		return lexHistogram
 	case r == 'x':
 		l.emit(TIMES)
 		return lexNumber
@@ -568,10 +568,16 @@ Loop:
 					return lexHistogram
 				}
 				l.errorf("missing `:` for histogram descriptor")
-			} else {
+				break Loop
-				l.errorf("bad histogram descriptor found: %q", word)
 			}
-
+			// Current word is Inf or NaN.
+			if desc, ok := key[strings.ToLower(word)]; ok {
+				if desc == NUMBER {
+					l.emit(desc)
+					return lexHistogram
+				}
+			}
+			l.errorf("bad histogram descriptor found: %q", word)
 			break Loop
 		}
 	}

promql/parser/lex_test.go

@@ -561,6 +561,35 @@ var tests = []struct {
 				},
 				seriesDesc: true,
 			},
+			{ // Series with sum as -Inf and count as NaN.
+				input: `{} {{buckets: [5 10 7] sum:Inf count:NaN}}`,
+				expected: []Item{
+					{LEFT_BRACE, 0, `{`},
+					{RIGHT_BRACE, 1, `}`},
+					{SPACE, 2, ` `},
+					{OPEN_HIST, 3, `{{`},
+					{BUCKETS_DESC, 5, `buckets`},
+					{COLON, 12, `:`},
+					{SPACE, 13, ` `},
+					{LEFT_BRACKET, 14, `[`},
+					{NUMBER, 15, `5`},
+					{SPACE, 16, ` `},
+					{NUMBER, 17, `10`},
+					{SPACE, 19, ` `},
+					{NUMBER, 20, `7`},
+					{RIGHT_BRACKET, 21, `]`},
+					{SPACE, 22, ` `},
+					{SUM_DESC, 23, `sum`},
+					{COLON, 26, `:`},
+					{NUMBER, 27, `Inf`},
+					{SPACE, 30, ` `},
+					{COUNT_DESC, 31, `count`},
+					{COLON, 36, `:`},
+					{NUMBER, 37, `NaN`},
+					{CLOSE_HIST, 40, `}}`},
+				},
+				seriesDesc: true,
+			},
 		},
 	},
 	{