BoundaryML/baml · error

Property not found: {} in class {}

Error message

Property not found: {} in class {}

What it means

ClassBuilder::property looks up an existing property to modify. If the property is not present in the IR's class definition (find_field returns None) and not otherwise resolvable, it bails with 'Property not found'. Only properties that already exist can be retrieved this way; new ones must be added with add_property.

Source

Thrown at engine/language_client_cffi/src/raw_ptr_wrapper/type_builder/objects.rs:356

        prop.lock().unwrap().set_type(field_type);
        Ok(self.create_property(name, rt))
    }

    pub fn property(&self, rt: &BamlRuntime, name: &str) -> anyhow::Result<ClassPropertyBuilder> {
        self.mode.at_least(NodeRW::ReadOnly)?;
        let cls = self.cls(rt)?;

        let builder = cls.lock().unwrap();
        match builder.maybe_get_property(name) {
            Some(_) => Ok(self.create_property(name, rt)),
            None => {
                // if the IR has the property, then its valid to add it again
                if let Ok(cls) = rt.ir.find_class(self.class_name.as_str()) {
                    if cls.find_field(name).is_some() {
                        let _ = builder.upsert_property(name);
                        Ok(self.create_property(name, rt))
                    } else {
                        anyhow::bail!("Property not found: {} in class {}", name, self.class_name)
                    }
                } else {
                    anyhow::bail!("Property not found: {} in class {}", name, self.class_name)
                }
            }
        }
    }

    pub fn is_from_ast(&self, rt: &BamlRuntime) -> anyhow::Result<bool> {
        self.mode.at_least(NodeRW::ReadOnly)?;
        Ok(rt.ir.find_class(self.class_name.as_str()).is_ok())
    }
}

#[derive(Debug, Clone)]
pub struct ClassPropertyBuilder {
    type_builder: RuntimeTypeBuilder,
    class_name: String,

View on GitHub (pinned to bd85ce9dee)

Solutions

1. Add the property first with cb.add_property(rt, name, type) before lookup
2. Verify the exact property name against the class definition (case-sensitive)
3. Use list_properties to confirm the field exists before lookup

Example fix

// before
let p = cb.property(rt, "nmae")?; // typo -> not found
// after
let p = match cb.property(rt, "name") {
    Ok(p) => p,
    Err(_) => cb.add_property(rt, "name", tb.string_type())?,
};

# check before lookup
if "name" not in cb.list_properties(rt):
    cb.add_property(rt, "name", tb.string())

try:
    p = cb.property(rt, name)
except Exception as e:
    if "not found" in str(e):
        cb.add_property(rt, name, ty)
        p = cb.property(rt, name)
    else:
        raise

When it happens

Trigger: Calling cb.property(rt, "field") for a property name that the class does not define, whether from a typo or because the property was never added.

Common situations: Typo in property name; calling .property() before add_property(); the property was removed/renamed in the BAML source while builder code still references the old name.

Related errors

• Class with name {name} does not exist
• Class not found: {}
• Property already exists: {} in class {}
• Class {} not found
• Class with name {name} already exists

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/85e74ea4c6694241. Report an issue: GitHub.