astrid-runtime/astrid · error

Cargo rustflags array contains a non-string value in {}

Error message

Cargo rustflags array contains a non-string value in {}

What it means

Array element validation in parse_rustflags: the rustflags value is an array, but one of its elements is not a string (e.g. an integer or nested array). Each array element must be an individual compiler flag string; a non-string element makes the flag list uninterpretable and absorb_document aborts naming the config file.

Source

Thrown at crates/astrid-build/src/rust/config.rs:406

        Ok(content) => Ok(Some(content)),
        Err(error) if error.kind() == std::io::ErrorKind::NotFound => Ok(None),
        Err(error) => Err(error)
            .with_context(|| format!("Failed to read Cargo configuration {}", path.display())),
    }
}

struct ParsedRustflags {
    flags: Vec<String>,
    is_array: bool,
}

fn parse_rustflags(item: &toml_edit::Item, path: &Path) -> Result<ParsedRustflags> {
    if let Some(array) = item.as_array() {
        let flags = array
            .iter()
            .map(|value| {
                value.as_str().map(str::to_owned).ok_or_else(|| {
                    anyhow::anyhow!(
                        "Cargo rustflags array contains a non-string value in {}",
                        path.display()
                    )
                })
            })
            .collect::<Result<Vec<_>>>()?;
        return Ok(ParsedRustflags {
            flags,
            is_array: true,
        });
    }
    if let Some(value) = item.as_str() {
        return Ok(ParsedRustflags {
            flags: value.split_whitespace().map(str::to_owned).collect(),
            is_array: false,
        });
    }
    bail!(

View on GitHub (pinned to affd8760f4)

Solutions

1. Quote every element of the rustflags array
2. Remove or stringify non-string elements
3. Alternatively use the string form `rustflags = "flag1 flag2"` if supported

Example fix

# before
[build]
rustflags = ["-C", "target-cpu", 4]
# after
[build]
rustflags = ["-C", "target-cpu=native"]

fn validate_rustflags(item: &toml_edit::Item) -> Result<(), String> {
    if let Some(arr) = item.as_array() {
        for v in arr.iter() {
            if v.as_str().is_none() {
                return Err("all rustflags array elements must be strings".into());
            }
        }
    }
    Ok(())
}

fn rustflags_all_strings(item: &toml_edit::Item) -> bool {
    item.as_array().map_or(true, |a| {
        a.iter().all(|v| v.as_str().is_some())
    })
}

match absorb_document(...) {
    Err(e) if e.to_string().contains("rustflags array contains a non-string") => {
        eprintln!("quote every element in the rustflags array");
    }
    other => other?,
}

When it happens

Trigger: absorb_document parsing `[build]\nrustflags = ["-C", "target-feature=+atomics", 42]` — any non-string array element triggers the error.

Common situations: Unquoted numeric-looking flags (e.g. -C link-arg=-O2 values left bare), copy-paste from JSON where numbers weren't quoted, mixing flags arrays with scalar forms.

Understand the failure class

Background: "Invalid value" and "allowed values are" config errors: what your library rejected and how to fix it — this error's family across 41 libraries.

Related errors

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• No Cargo build target selected. Set `[build] target = "wasm3

AI-assisted analysis of astrid-runtime/astrid@affd8760f4 (2026-09-09). Data as JSON: /api/errors/64c1849a6ea29bb5. Report an issue: GitHub.