R. Saadia Gaon explains (Emunot V’Deiot 3:5) that Yonah had fulfilled his mission:

If, furthermore, one were to ask, “But how was it that Jonah was chosen to carry out a mission from which he ran away, when it would seem that the All-Wise would not choose anyone who would disobey him?” I would answer that I have gone over the story of Jonah repeatedly and yet have not found a single verse that would state explicitly that he did not fulfill his first mission. And although I have not found a definite indication that he carried it out either, yet I feel constrained to believe that he did, in the same manner in which all the prophets did. Another reason is that the All-Wise would not choose anyone to execute an errand of His who would not carry it out. Besides, I find Scripture saying constantly: And the Lord spoke unto Moses, saying: Speak unto the children of Israel (Lev. 23:1, 2). Yet it is only in a few instances that the comment was made that the command was carried out, as it is done [in the statement]: And Moses spoke so unto the children of Israel (Exod. 6:9).

 

What Jonah fled from was only the possibility of his being sent on a mission a second time. For it seemed to him that his first mission constituted a warning, but that the second was an act of intimidation and a threat. He was, therefore, afraid that, after his having threatened them with some punishment or other, those to whom he would be sent would repent so that the threat would not be carried out and it would be said that it was due to his having lied. Hence he departed from the land which the Creator had appointed to be the seat of prophecy.

 

All this is explicitly stated at the end of Jonah’s remark: I pray Thee, O Lord was not this my saying, when I was yet in mine own country? Therefore I fled beforehand into Tarshish (Jonah 4:2). No sin attached to him, therefore, since his Lord had not told him: “I am going to send thee a second time.” That was merely a thought that had arisen in his mind, and he rejected what might perhaps come or not come to pass. Thereupon God made him return by compulsion to the country that had been singled out for prophecy, and brought him to the point of prophesying, and sent him forth on his mission and thus executed [the plan conceived by] His wisdom.

 

(Rosenblatt translation p. 153-154)

R. Saadia Gaon explains (Emunot V’Deiot 3:5) that Yonah had fulfilled his mission:

If, furthermore, one were to ask, “But how was it that Jonah was chosen to carry out a mission from which he ran away, when it would seem that the All-Wise would not choose anyone who would disobey him?” I would answer that I have gone over the story of Jonah repeatedly and yet have not found a single verse that would state explicitly that he did not fulfill his first mission. And although I have not found a definite indication that he carried it out either, yet I feel constrained to believe that he did, in the same manner in which all the prophets did. Another reason is that the All-Wise would not choose anyone to execute an errand of His who would not carry it out. Besides, I find Scripture saying constantly: And the Lord spoke unto Moses, saying: Speak unto the children of Israel (Lev. 23:1, 2). Yet it is only in a few instances that the comment was made that the command was carried out, as it is done [in the statement]: And Moses spoke so unto the children of Israel (Exod. 6:9).

What Jonah fled from was only the possibility of his being sent on a mission a second time. For it seemed to him that his first mission constituted a warning, but that the second was an act of intimidation and a threat. He was, therefore, afraid that, after his having threatened them with some punishment or other, those to whom he would be sent would repent so that the threat would not be carried out and it would be said that it was due to his having lied. Hence he departed from the land which the Creator had appointed to be the seat of prophecy.

All this is explicitly stated at the end of Jonah’s remark: I pray Thee, O Lord was not this my saying, when I was yet in mine own country? Therefore I fled beforehand into Tarshish (Jonah 4:2). No sin attached to him, therefore, since his Lord had not told him: “I am going to send thee a second time.” That was merely a thought that had arisen in his mind, and he rejected what might perhaps come or not come to pass. Thereupon God made him return by compulsion to the country that had been singled out for prophecy, and brought him to the point of prophesying, and sent him forth on his mission and thus executed [the plan conceived by] His wisdom.

(Rosenblatt translation p. 153-154)