empty array recognized as null in http request

[zjh25]

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Dify version

1.13.3

Cloud or Self Hosted

Self Hosted (Docker)

Steps to reproduce

When using the raw JSON format in the HTTP Request node to send POST requests,if I reference a variable from the previous node whose value is an empty list [],the empty list will be rendered as blank content in the final request body.
This causes invalid JSON format (extra illegal comma),triggers a 400 parameter parsing error and request failure.

✔️ Expected Behavior

Success request

❌ Actual Behavior

No response

[zjh25]

[dosubot]

Hi @zjh25! I'm Dosu and I’m helping the dify team.

This is a confirmed behavior in how the VariablePool handles empty arrays during template substitution. When an empty list [] is substituted into a JSON body template, the ArrayAnySegment (and related array segment types) converts it to an empty string "" rather than the JSON representation "[]" [1]. This means a template like:

{"items": {{#node.myArray#}}, "count": 5}

becomes:

{"items": , "count": 5}

…which is invalid JSON, causing the 400 error you're seeing. The JSON repair mechanism runs after substitution [2] but can't fix this kind of structural issue.

There are a couple of related PRs working toward improving this area — PR #32317 adds proper JSON encoding for template values, and PR #34185 extends the HTTP body editor to better support array/object variable references [3] [4].

Workaround for now: Use a Code node before the HTTP Request node to serialize the array to a JSON string explicitly:

import json

def main(my_array: list) -> dict:
    return {"json_array": json.dumps(my_array if my_array else [])}

Then reference {{#code_node.json_array#}} in your HTTP Request body. This ensures empty arrays are properly rendered as [] in the final JSON.

To reply, just mention @dosu.

---

Docs are dead. Just use Dosu.

[zjh25]

Hi @zjh25! I'm Dosu and I’m helping the dify team.

This is a confirmed behavior in how the VariablePool handles empty arrays during template substitution. When an empty list [] is substituted into a JSON body template, the ArrayAnySegment (and related array segment types) converts it to an empty string "" rather than the JSON representation "[]" [1]. This means a template like:

{"items": {{#node.myArray#}}, "count": 5}
becomes:

{"items": , "count": 5}
…which is invalid JSON, causing the 400 error you're seeing. The JSON repair mechanism runs after substitution [2] but can't fix this kind of structural issue.

There are a couple of related PRs working toward improving this area — PR #32317 adds proper JSON encoding for template values, and PR #34185 extends the HTTP body editor to better support array/object variable references [3] [4].

Workaround for now: Use a Code node before the HTTP Request node to serialize the array to a JSON string explicitly:

import json

def main(my_array: list) -> dict:
return {"json_array": json.dumps(my_array if my_array else [])}
Then reference {{#code_node.json_array#}} in your HTTP Request body. This ensures empty arrays are properly rendered as [] in the final JSON.

To reply, just mention @dosu.

Docs are dead. Just use Dosu.

But In Dify v1.11, this problem does not exist. why?