fix(json): bug when \uxxxx is first escaping sequence in a string

Signed-off-by: Maxime Soulé <btik-git@scoubidou.com>

Author: maxatome

internal/json/lex.go

@@ -311,8 +311,8 @@ str:
 				if j.remain() >= 5 {
 					r, ok = hex(j.buf[j.pos.bpos+1 : j.pos.bpos+5])
 					if ok {
-						j.pos = j.pos.incHoriz(4)
 						appendBuffer(r)
+						j.pos = j.pos.incHoriz(4)
 						break
 					}
 				}

internal/json/parser_test.go

@@ -35,7 +35,27 @@ func TestJSON(t *testing.T) {
 			`0`,
 			`""`,
 			`"123.456$"`,
-			` "foo bar \" \\ \/ \b \f \n\r \t \u10e6 \u10E6 héhô" `,
+			` "foo bar \" \\ \/ \b \f \n\r \t \u20ac \u10e6 \u10E6 héhô" `,
+			`"\""`,
+			`"\\"`,
+			`"\/"`,
+			`"\b"`,
+			`"\f"`,
+			`"\n"`,
+			`"\r"`,
+			`"\t"`,
+			`"\u20ac"`,
+			`"zz\""`,
+			`"zz\\"`,
+			`"zz\/"`,
+			`"zz\b"`,
+			`"zz\f"`,
+			`"zz\n"`,
+			`"zz\r"`,
+			`"zz\t"`,
+			`"zz\u20ac"`,
+			`["74.99 \u20ac"]`,
+			`{"text": "74.99 \u20ac"}`,
 			`[ 1, 2,3, 4 ]`,
 			`{"foo":{"bar":true},"zip":1234}`,
 		} {