Feature request: introduce ONode.closestMatch(jsonPath)

[arcuri82]

Hi,

again, thanks for maintaining this library! ;)

I am dealing with the following case:

node.exists(jsonPath)

where jsonPath is given as input by the user.
The path must match something in the tree.
If not, it is a user error.
However, for users it might be difficult to debug what they are doing wrong when writing the paths.
They just get a false on the exists() calls.
To help my users, I need to give them some hints on what they are doing wrong.

My idea was to tell them what is the "closest" match for their queries.
For example, consider the following path on an OpenAPI schema:

jsonPath = $.paths["/api"].post.parameters[?(@.name=="x")]

the user gets node.exists(jsonPath) == false, as they made a mistake, because there is no post and rather they meant a get.

Would be good to have something like:

node.closestMatch(jsonPath) == $.paths["/api"]

so they can understand that their problem starts with the .post part.

To achieve this, the jsonPath needs to be split in tokens, and then apply exists() on shorter and shorter paths until true is returned.

Do you think you could add such feature?
Or is there already something in the library that could be used to achieve this?

many thanks!

[noear]

Great idea! Just submit the PR directly, please : )

---

好想法。你可以直接提交个 pr ：）

[noear]

Perhaps it would also be possible to create a tool class on the application side to handle this task.

---

或许也可以在应用侧包装一个工具类，做这个活。

[arcuri82]

is there already some utility class in the library for which, given a jsonPath string, it returns an array of tokens, e.g., "$", ".paths", "[\"/api\"]", ".post", ".parameters", "[?(@.name==\"x\")]".
if yes, then it would be trivial to implement such function.
i assume somewhere you already needed to parse the jsonPath string anyway, isn't it?

[noear]

This does exist and it can analyze the path segments.

---

这个确实有，会分析路径段。

---

示例：

JsonPath jsonPath = JsonPath.parse(...);

jsonPath.getSegments(); //List<Segment> segments

[arcuri82]

great! I can check it out, and see to make a PR today or later in the week ;)

[noear]

我再给 JsonPath 加个能力，方便生成子级 JsonPath 实例。比如：$.o['j j']['k.k']（有三段） 的 JsonPath 实例，可以快速获取一段（$.o） 和 二段（$.o['j j']）的实例

[noear]

新加了 JsonPath:subPath 方法。你可以基于它包装一个工具类（在应用侧）

---

使用示例：

ONode oNode = ONode.ofJson("...");

JsonPath jsonPath = JsonPath.parse("...");
if (jsonPath.select(oNode).isEmpty()) { //like exists
    if (jsonPath.subPath(jsonPath.getSegmentCount() - 1).select(oNode).isEmpty()) {

    }
}

[arcuri82]

great, thx

[arcuri82]

do you still want me to write a PR for the closestMatch() function, or should I just implement it and use it in my project without making a PR here?

[noear]

如果应用侧能通过工具包装解决，就不需要 PR 了（这种需求太少了）

[arcuri82]

ok, thx. i ll implement it on my client side. i ll let you know if there is any issue with it

[noear]

你们在做什么项目啊？对 Jsonpath 的应用，很全面。

[arcuri82]

I am using it to handle pointers in OpenAPI Initiative Overlay support, in the library overlay-jvm, which itself is used in the fuzzer EvoMaster

[arcuri82]

following seems working, at least in initial tests:

    /**
     *  Given an input jsonpath, finds the closest match in the current tree.
     *  If no target node exists for the jsonpath, this function looks at the jsonpath
     *  without its last token, making the jsonpath shorter.
     *  For example, if '$.a.b.c' matches nothing, the next path that is checked is '$.a.b'.
     *  This process is repeated recursively until a reduced jsonpath is found for which at
     *  least one node is found.
     *  <p>
     *  Note that 'n.exists(p) == true' implies 'n.closestMatch(p) == p'.
     */
    public static String closestMatch(ONode root, String jsonpath) {
        if(jsonpath.isEmpty()) {
            return "";
        }

        JsonPath path = JsonPath.parse(jsonpath);
        if(!path.select(root).isEmpty()){
            return jsonpath;
        }

        while(path.getSegmentCount() > 1) {
            path = path.subPath(path.getSegmentCount() - 1);
            if(!path.select(root).isEmpty()){
                return path.getExpression();
            }
        }

        return "";
    }