What causes "affine not an array." in flxzt/rnote?

Inspect the offending JSON at the reported path and change "affine" to a JSON array of 6 numbers, e.g. [1,0,0,1,0,0].

flxzt/rnote · error · anyhow::Error

affine not an array.

Error message

affine not an array.

What it means

Thrown by convert_transform_to_affine_in_obj during the maj0min15 file-format migration when a transform JSON object's "affine" key exists but is not a JSON array. The migration needs to read the 6 affine matrix elements by index, so it requires an array. Rnote files carry transforms serialized as JSON inside the document; a malformed or hand-edited file triggers this.

Solutions

Inspect the offending JSON at the reported path and change "affine" to a JSON array of 6 numbers, e.g. [1,0,0,1,0,0].
Regenerate the file from a working version of the app or from a backup instead of repairing it manually.
Fix the generating code so it serializes affine as an array (serde serializes a [f64;6]/Vec as a JSON array).

Example fix

// before (invalid file JSON)
"transform": { "affine": "1,0,0,1,0,0" }
// after
"transform": { "affine": [1, 0, 0, 1, 0, 0] }

Defensive patterns

Strategy: validation

Validate before calling

let t = doc.get("transform").and_then(|v| v.as_object())?;
if t.get("affine").and_then(|a| a.as_array()).map(|a| a.len() >= 8) != Some(true) {
    return Err("invalid transform.affine: expected array of >= 8 numbers");
}

Type guard

fn is_valid_affine(v: &serde_json::Value) -> bool {
    v.get("affine").and_then(|a| a.as_array())
        .map(|a| a.len() >= 8 && a.iter().all(|e| e.is_number()))
        .unwrap_or(false)
}

Prevention

Validate .rnote file JSON against the expected schema before running migrations.
Never hand-edit serialized snapshot JSON; use the app's own save path.
Keep file producers on the same serializer version as consumers.

When it happens

Trigger: Opening/converting an .rnote file whose JSON contains an object entry with a "transform" object where "affine" is a non-array JSON value (number, string, null, object) instead of a 6+ element array.

Common situations: Hand-edited or programmatically generated .rnote files, truncated/corrupted downloads, or files produced by an incompatible writer version.

Understand the failure class

Background: "is not a compatible type" / "cannot merge" errors: when a value's type doesn't match what the library requires — this error's family across 65 libraries.

Related errors

AI-assisted analysis of flxzt/rnote@bbc5354502 (2026-09-08). Data as JSON: /api/errors/4d2bc2d7077a74b7. Report an issue: GitHub.

Appendix: source

Thrown at crates/rnote-engine/src/fileformats/rnoteformat/maj0min15.rs:131

    }
}

/// Converts a "object->transform->nalgebra-affine" to "object->(glamx-)affine"
fn convert_transform_to_affine_in_obj(obj: &mut IValue) -> anyhow::Result<()> {
    let obj = obj
        .as_object_mut()
        .ok_or(anyhow!("supplied value is not a JSON object."))?;
    let transform = obj
        .remove("transform")
        .ok_or(anyhow!("rect does not contain 'transform'."))?;
    let transform = transform
        .as_object()
        .ok_or(anyhow!("transform is not a JSON object."))?;
    let affine = transform
        .get("affine")
        .ok_or(anyhow!("transform does not contain 'affine'."))?
        .as_array()
        .ok_or(anyhow!("affine not an array."))?;

    obj.insert(
        "affine",
        vec![
            #[allow(clippy::get_first)]
            affine
                .get(0)
                .cloned()
                .ok_or(anyhow!("affine does not have value at index 0"))?,
            affine
                .get(1)
                .cloned()
                .ok_or(anyhow!("affine does not have value at index 1"))?,
            affine
                .get(3)
                .cloned()
                .ok_or(anyhow!("affine does not have value at index 3"))?,
            affine

View on GitHub (pinned to bbc5354502)