jmespath/chat

Alestor

@Alestor

Same Problem with contains

If I use the not-expression on grades I'll get the entire list back. No matter if I use contains or starts_with

hell-racer

@hell-racer

With 'a':

list[?grades[?@ == 'a']].student

Without 'a':

list[?!(grades[?@ == 'a'])].student

Using contains:

list[?contains(grades, 'a')].student
list[?!(contains(grades, 'a'))].student

Alestor

@Alestor

makes sense, thank you again :)

fireundubh

@fireundubh

just wanted to say the above example with the @ token was really helpful and should be on the Examples page

Stephane Landelle

@slandelle

Hi there,

I have a question regarding literal wrapping.
According to the JMESPATH specification, the wrapping character is supposed to be backtick:

literal           = "`" json-value "`"

However, I see lots of examples in this chat using simple quotes and backticks interchangeably.
And indeed the JMESPath implementation used in the online evaluator supports simple quotes as well.

But then, other implementations don't, eg the Java one.

IMHO, this is a bug and all implementations should strictly abide to the specification (that's the whole point of JMESPath compared to JsonPath).

(original discussing here: https://community.gatling.io/t/jmespath-is-not-finding-a-json-object/6995)

Thoughts?

hell-racer

@hell-racer

Hi! Can you please provide an example of single quotes used for json literals?

Stephane Landelle

@slandelle

@hell-racer There's one in the Gatling forum post I provided.

{
"status":"GOOD",
"fruits":[
  {
    "name":"Apple",
    "details": {
       "size":500
      }
  },
  {
    "name":"Cherry",
    "details": {
        "size":100
      }
  }]
}

On https://jmespath.org/, both following expressions work.

With quotes:

fruits[?details.size >= '500']

With backticks:

fruits[?details.size >= `500`]

Only the latter would work with https://github.com/burtcorp/jmespath-java

hell-racer

@hell-racer

Yeah... I meant some examples of single quotes in such context in JmesPath documentation.

Anyway, in my opinion, it should return empty array when filtering by '500' while the values are numbers in source data.

Stephane Landelle

@slandelle

Yeah... I meant some examples of single quotes in such context in JmesPath documentation.

I don't think there's one. The documentation matches with the specification.

Anyway, in my opinion, it should return empty array when filtering by '500' while the values are numbers in source data.

Agree. I would have liked to open an issue against the JMESPath implementation used for the online evaluator on https://jmespath.org/ but I don't know which one it is. Do you know?

hell-racer

@hell-racer

I think that's https://github.com/jmespath/jmespath.site

@springcomp I summon you :)

Stephane Landelle

@slandelle

https://github.com/jmespath/jmespath.site/blob/master/docs/_static/js/jmespath.min.js

It's the JavaScript implementation. I'm going to open an issue on its GitHub project. Thanks a lot for your help!

Stephane Landelle

@slandelle

For the record: jmespath/jmespath.js#85

hell-racer

@hell-racer

Thanks!

Maxime Labelle

@springcomp

@slandelle you are right, you are not crazy 😁.

For the record, JMESPath used to support strings using this syntax: `this was a string` .
However, JEP-12 made this syntax obsolete.

Now, the grammar is much clearer. You can only have:

quoted-string : simple JSON strings easy to input using simple quotes. e.g 'hello world!'.
raw-string literals : JSON values typed verbatim (except, backtick must be escaped). e.g `"{}`" would be an empty JSON object. Please, note that a JSON string has surrounding double quotes, and thus mus be input like so `"this is a string"` .

The JavaScript implementation did not change as part of JEP-12 and supports both the old and new way of expressing strings. I suspect this is for compatibility reasons.

Maxime Labelle

@springcomp

Your question is raised in the context of numeric literals. JMESPath does not support JSON numbers in its grammar. So those must be input using raw-string literals. Thus:

fruits[? details.size >= `500` ] filters all fruits whose size is greater than number 500.
fruits[? details.size >= '500' ] filters all fruits whose size is greater than string "500". Probably not what you want.

Comparisons between numbers and strings is currently undefined in the grammar as ordering operators are only valid between two numbers. However, popular implementations do make some attempt to cast the string to a number before performing the comparison, so it mostly works even though it is not standards-compliant.

Blaine Morgan

@nbmorgan

Newbie question: What does JMES stand for?

hell-racer

@hell-racer

https://jmespath.org/contents.html
"JSON Matching Expression paths"

Nolan Woods

@innovate-invent

the authors name is also James

Maxime Labelle

@springcomp

@/all we are making good progress trying to standardize some improvements to JMESPath. Please, feel free to share your feedback and comments.

Stephane Landelle

@slandelle

Comparisons between numbers and strings is currently undefined in the grammar as ordering operators are only valid between two numbers. However, popular implementations do make some attempt to cast the string to a number before performing the comparison, so it mostly works even though it is not standards-compliant.

If you guys are considering JMESPath 2.0, should this String comparison be made a standard?

Maxime Labelle

@springcomp

@slandelle I have specified your request. However, I’m not sure I agree with implicit conversions, after all...

msouilhi

@msouilhi

I would extract the keys for this dictionnary to get kas_sub.med , kas_sub.test

{
 "FACTS_ENTRY": {
        "kas_sub.med":  "true",
        "kas_sub.test":  "true"
}

Nolan Woods

@innovate-invent

@msouilhi https://jmespath.site/#func-keys

msouilhi

@msouilhi

@innovate-invent i am using it inside a playbook in ansible and i am new to jmespath so i would use it like this keys(FACTS_ENTRY)?

hell-racer

@hell-racer

Yep

(probably you've tried it at https://jmespath.org/ and it didn't work because you missed one closing curly brace in your input json)

msouilhi

@msouilhi

thank you so much guys i will try it right now

hansenjohansen

@hansenjohansen:matrix.org

[m]

I've got a JSON output that looks like the (simplified) below:

{
"Code": 1000,
"GlobalServers": [
{
"Name": "bar",
"Country": "IS",
"Status": 1,
"Servers": [
{
"Name": "foo",
"Status": 1
}
]
}
]
}

But I am struggling to filter it.
GlobalServers[?Status==1].... works
but then if I try
GlobalServers[?Status==1].Servers[?Status==1] ...I get no ouput

hell-racer

@hell-racer

Hi! At this point

GlobalServers[?Status==`1`].Servers

... you have an array of arrays:

[
  [
    {
      "Name": "foo",
      "Status": 1
    }
  ]
]

So you have to flatten it and stop the projection before filtering:

GlobalServers[?Status==`1`].Servers[]|[?Status==`1`]

Output:

[
  {
    "Name": "foo",
    "Status": 1
  }
]

hansenjohansen

@hansenjohansen:matrix.org

[m]

I see, that makes sense. Thanks for the clear explanationhell-racer (hell-racer) . So I guess the only issue then is that if I flatten it, I loose the ability to get a key value from the parent ? (e.g. if I wanted to pull "Country" value from the parent in addition to the data from the filtered child nodes)

hell-racer

@hell-racer

It could be possible to filter while keeping nesting level. Just post exact shape of output you need (based on input you've posted), and I'll try to come up with the query.

hell-racer

@hell-racer

If you need just the Servers and Country:

GlobalServers[?Status==`1`].{ Servers: Servers[?Status==`1`], Country: Country }

If you need everything while filtering both levels:

GlobalServers[?Status==`1`].merge(@, { Servers: Servers[?Status==`1`] })

hansenjohansen

@hansenjohansen:matrix.org

[m]

Sorry for the delay in reply @hell-racer , I'll go test these and let you know.

hansenjohansen

@hansenjohansen:matrix.org

[m]

@hell-racer: The suggestion with merge(@) worked great. Thank you again !

hell-racer

@hell-racer

nice :)

hansenjohansen

@hansenjohansen:matrix.org

[m]

@hell-racer: There's one more thing, I was hoping to find the answer myself but I can't find the right way to do it. Building on your "GlobalServers[?Status==1].merge(@, { Servers: Servers[?Status==1] })".....

The GlobalServers parent node has a "score" value for each entry, I would like to only return the node for the highest score (that also matches the filter).

So far the nearest I have managed to get is this:
"max_by(GlobalServers[],&Score).merge(@, { Servers: Servers[?Status==1] })"

But no matter how I try to integrate the original GlobalServers filter, I can't manage do to it. I've tried putting max_by() before the filter, after the filter, inside the filter ... jmespath complains each time.

I'm sure I'm missing something simple !

hell-racer

@hell-racer

Can you post source data with all the fields involved?

hansenjohansen

@hansenjohansen:matrix.org

[m]

@hell-racer: Sure. Lucky for you it's coming from a public API, so fill your boots ... https://api.protonmail.ch/vpn/logicals

hell-racer

@hell-racer

It returns ERR_CONNECTION_RESET :(.
Ok, on the site https://jmespath.org/ given input:

{
    "Code": 1000,
    "GlobalServers": [
        {
            "Name": "bar1",
            "Country": "IS",
            "Score": 1,
            "Servers": [
                {
                    "Name": "foo1",
                    "Status": 1
                },
                {
                    "Name": "foo2",
                    "Status": 2
                }
            ]
        },
        {
            "Name": "bar2",
            "Country": "US",
            "Score": 2,
            "Servers": [
                {
                    "Name": "foo",
                    "Status": 1
                },
                {
                    "Name": "foo2",
                    "Status": 2
                }
            ]
        }        
    ]
}

Your query:

max_by(GlobalServers, &Score).merge(@, { Servers: Servers[?Status==`1`] })

Returns:

{
  "Name": "bar2",
  "Country": "US",
  "Score": 2,
  "Servers": [
    {
      "Name": "foo",
      "Status": 1
    }
  ]
}

So if it doesn't work in your environment, probably there is a problem with specific JmesPath implementation.

Ah, maybe you have unnecessary [] in the GlobalServers[].

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