Condition function len() counting number of characters in string?

[salim-b]

The condition function len()'s description reads:

Returns the length of the object/slice. Works only with the [BODY] placeholder.

So to my understanding, len() should return the number of elements the specified object or slice contains. But with atomic strings, it seems to count the number of characters instead.

Consider the following JSON:

[{
  "name": "hugo",
  "email": "",
  "permissions": [{
    "capability": {
      "Update": {}
    },
    "component": "/api/v1/organisation/b6f0c4ca-1f22-40ef-baae-f31ec52f558b"
  }, {
    "capability": {
      "Read": {}
    },
    "component": "/api/v1/organisation/b6f0c4ca-1f22-40ef-baae-f31ec52f558b"
  }, {
    "capability": {
      "Delete": {}
    },
    "component": "/api/v1/organisation/b6f0c4ca-1f22-40ef-baae-f31ec52f558b"
  }, {
    "capability": {
      "Create": {}
    },
    "component": "/api/v1/organisation/b6f0c4ca-1f22-40ef-baae-f31ec52f558b"
  }]
}, "blabla-Hugo"]

Running the condition test len([BODY][0].name) == 1 against the above payload fails, suggesting the actual length would be 4, not 1.

Is this the intended behaviour? If so, the README should be clearer on this, I guess.

[TwiN]

This is the intended behavior.

If the target JSON path is an array, it will return the length of the array, while if it is anything else, it will consider it as a string and return the length of the string.

[salim-b]

Thanks for the reply!

If the target JSON path is an array, it will return the length of the array, while if it is anything else, it will consider it as a string and return the length of the string.

The last part of that sentence doesn't seem to be entirely true. My observations so far:

1. A condition test len([BODY]) leads to a panic: interface conversion: interface {} is []interface {}, not map[string]interface {}:

   logs

   2022-11-18T16:16:12Z   [info]panic: interface conversion: interface {} is map[string]interface {}, not []interface {}
   2022-11-18T16:16:12Z   [info]goroutine 146 [running]:
   2022-11-18T16:16:13Z   [info]	ithub.com/TwiN/gatus/v4/jsonpath.extractValue({0xc00004242a, 0x3}, {0xc02dc0?, 0xc0001ffaa0})
   2022-11-18T16:16:13Z   [info]	/app/jsonpath/jsonpath.go:84 +0x4b8
   2022-11-18T16:16:13Z   [info]	ithub.com/TwiN/gatus/v4/jsonpath.walk({0xc00004242a, 0x3}, {0xc02dc0, 0xc0001ffaa0})
   2022-11-18T16:16:13Z   [info]	/app/jsonpath/jsonpath.go:40 +0x32f
   2022-11-18T16:16:13Z   [info]	/app/jsonpath/jsonpath.gosonpath.walk({0xc00004242a, 0x3}, {0xbcb440, 0xc0003eda88})
   2022-11-18T16:16:13Z   [info]github.com/TwiN/gatus/v4/jsonpath.Ev
   2022-11-18T16:16:13Z   [info]	/app/jsonpath/jsonpath.go:18path.Ev
   l({0xc00004242a, 0x3}, {0xc0004f1c00, 0x202, 0x380})
   2022-11-18T16:16:13Z   [info]	/app/jsonpath/jsonpath.go:18 +0x9c
   2022-11-18T16:16:13Z   [info]	ithub.com/TwiN/gatus/v4/core.sanitizeAndResolve({0xc0000786e0, 0x2, 0xcb85f1?}, 0xc000226240)
   2022-11-18T16:16:13Z   [info]github.com/TwiN/gatus/v4/core.Cond
   2022-11-18T16:16:13Z   [info]	ithub.com/TwiN/gatus/v4/core.Cond
   tion.evaluate({0xc000042420, 0x13}, 0xc000226240, 0x0)
   2022-11-18T16:16:13Z   [info]	/app/core/condition.go:96 +0xa5
   2022-11-18T16:16:13Z   [info]	ithub.com/TwiN/gatus/v4/core.(*Endpoint).EvaluateHealth(0xc00019ed00)
   2022-11-18T16:16:13Z   [info]github.com/TwiN/gatus/v4/watchdog
   2022-11-18T16:16:13Z   [info]	ithub.com/TwiN/gatus/v4/watchdog
   execute(0xc00019ed00, 0xc00007e060?, 0xc000194a80, 0x0, 0x0, 0x0)
   2022-11-18T16:16:13Z   [info]github.com/TwiN/gatus/v4/watchdog.mo
   2022-11-18T16:16:13Z   [info]	/app/watchdog/watchdog.go:41 +0x5c
   created by 019ed00, 0xd4c870?, 0xe32970?, 0x0?, 0x16?, 0x3d?, {0xe32970, 0xc000195040})
   2022-11-18T16:16:13Z   [info]	/app/watchdog/watchdog.go:41 +0x5c
   2022-11-18T16:16:13Z   [info]	/app/watchdog/watchdog.go:33 +0x20dwatchdog.Monitor
   2022-11-18T16:16:13Z   [info]	/app/watchdog/watchdog.go:33 +0x20d
   

2. A condition test len([BODY][0]) leads to a panic: interface conversion: interface {} is map[string]interface {}, not []interface {}:

   logs

   2022-11-18T16:16:12Z   [info]panic: interface conversion: interface {} is map[string]interface {}, not []interface {}
   2022-11-18T16:16:12Z   [info]goroutine 146 [running]:
   2022-11-18T16:16:13Z   [info]	ithub.com/TwiN/gatus/v4/jsonpath.extractValue({0xc00004242a, 0x3}, {0xc02dc0?, 0xc0001ffaa0})
   2022-11-18T16:16:13Z   [info]	/app/jsonpath/jsonpath.go:84 +0x4b8
   2022-11-18T16:16:13Z   [info]	ithub.com/TwiN/gatus/v4/jsonpath.walk({0xc00004242a, 0x3}, {0xc02dc0, 0xc0001ffaa0})
   2022-11-18T16:16:13Z   [info]	/app/jsonpath/jsonpath.go:40 +0x32f
   2022-11-18T16:16:13Z   [info]	/app/jsonpath/jsonpath.gosonpath.walk({0xc00004242a, 0x3}, {0xbcb440, 0xc0003eda88})
   2022-11-18T16:16:13Z   [info]github.com/TwiN/gatus/v4/jsonpath.Ev
   2022-11-18T16:16:13Z   [info]	/app/jsonpath/jsonpath.go:18path.Ev
   l({0xc00004242a, 0x3}, {0xc0004f1c00, 0x202, 0x380})
   2022-11-18T16:16:13Z   [info]	/app/jsonpath/jsonpath.go:18 +0x9c
   2022-11-18T16:16:13Z   [info]	ithub.com/TwiN/gatus/v4/core.sanitizeAndResolve({0xc0000786e0, 0x2, 0xcb85f1?}, 0xc000226240)
   2022-11-18T16:16:13Z   [info]github.com/TwiN/gatus/v4/core.Cond
   2022-11-18T16:16:13Z   [info]	ithub.com/TwiN/gatus/v4/core.Cond
   tion.evaluate({0xc000042420, 0x13}, 0xc000226240, 0x0)
   2022-11-18T16:16:13Z   [info]	/app/core/condition.go:96 +0xa5
   2022-11-18T16:16:13Z   [info]	ithub.com/TwiN/gatus/v4/core.(*Endpoint).EvaluateHealth(0xc00019ed00)
   2022-11-18T16:16:13Z   [info]github.com/TwiN/gatus/v4/watchdog
   2022-11-18T16:16:13Z   [info]	ithub.com/TwiN/gatus/v4/watchdog
   execute(0xc00019ed00, 0xc00007e060?, 0xc000194a80, 0x0, 0x0, 0x0)
   2022-11-18T16:16:13Z   [info]github.com/TwiN/gatus/v4/watchdog.mo
   2022-11-18T16:16:13Z   [info]	/app/watchdog/watchdog.go:41 +0x5c
   created by 019ed00, 0xd4c870?, 0xe32970?, 0x0?, 0x16?, 0x3d?, {0xe32970, 0xc000195040})
   2022-11-18T16:16:13Z   [info]	/app/watchdog/watchdog.go:41 +0x5c
   2022-11-18T16:16:13Z   [info]	/app/watchdog/watchdog.go:33 +0x20dwatchdog.Monitor
   2022-11-18T16:16:13Z   [info]	/app/watchdog/watchdog.go:33 +0x20d
   

3. A len() condition test on a JSON Path that leads to an object (like len([BODY][0].permissions[0]) >= 1) or the null value results in an INVALID error like couldn't walk through 'JSON_PATH' because type was '<nil>', but expected 'map[string]interface{}.

4. A len() condition test on a JSON Path that leads to a number or boolean always returns 1, regardless of the actual value.

Are all of these observations the intended behaviour?

[TwiN]

They are not. Thank you for pointing this out; I'm working on a fix right now :)

[TwiN]

Resolved by #372