slint-ui/slint · error

License ` ` of crate is not in the accepted list

Error message

License `{expression}` of crate {} {} is not in the accepted list

What it means

The `xtask` license checker validates that every dependency crate's declared SPDX license expression is on the project's accepted-licenses list (with optional per-crate allow entries). When a crate's license is not accepted and not allowed, the `generate` step bails with this error. It guards the dependency set against licenses the project cannot ship.

Solutions

1. Add an allow entry for the package in xtask's license allow list if the license is acceptable for this use
2. Downgrade or pin the dependency to a version with an accepted license
3. Replace the dependency with an alternative that has an accepted license, or negotiate/approve the new license and add its SPDX id to the accepted list

Example fix

// before (allow list in xtask license.rs / config)
let allow = ""; // crate with ISC license not listed
// after
let pkg_allow = Some("ISC"); // explicit per-crate allow added for the new dependency

# Check a crate's license before adding it
cargo add foo --dry-run
grep '^license' $(cargo metadata ... | jq -r '.packages[] | select(.name=="foo") | .manifest_path')

When it happens

Trigger: Adding or upgrading a dependency whose Cargo.toml `license` field contains an SPDX expression not present in the accepted list and not covered by a per-package entry in the allow list; a dependency changing its license in a new version.

Common situations: `cargo xtask` license/dependency checks in CI after `cargo update` pulls a crate version with a new license; introducing a crate with a copyleft or nonstandard license.

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

Related errors

• Missing LICENSES directory for published crate
• Missing tag
• No license file found in root LICENSES/ for SPDX id
• unexpected header. expected
• cargo failed

AI-assisted analysis of slint-ui/slint@bb937076de (2026-09-16). Data as JSON: /api/errors/fd5f7a2d7aed4ee6. Report an issue: GitHub.

Appendix: source

Thrown at xtask/src/license.rs:161

        // Lax parsing accepts the deprecated `/` OR-separator and imprecise
        // identifiers (e.g. `apache2`) still found in older crates.
        let expr =
            spdx::Expression::parse_mode(&expression, spdx::ParseMode::LAX).with_context(|| {
                format!("Cannot parse license `{expression}` of {} {}", pkg.name, pkg.version)
            })?;

        // A `[package.metadata.slint-license.allow]` entry in the analyzed
        // crate's manifest extends the accepted set for *that one dependency
        // only*, so an exceptional license (e.g. LGPL-3.0 via dynamic linking)
        // is approved explicitly per-crate rather than relaxed project-wide.
        let pkg_allow = allow.get(pkg.name.as_str()).map(String::as_str);
        let pkg_accepted = |req: &spdx::LicenseReq| {
            let id = license_string(req);
            accepted.contains(id.as_str()) || pkg_allow == Some(id.as_str())
        };
        if !expr.evaluate(pkg_accepted) {
            bail!(
                "License `{expression}` of crate {} {} is not in the accepted list",
                pkg.name,
                pkg.version
            );
        }

        // Record the license ids the crate uses, so each gets a body.
        for req in expr.requirements() {
            if !pkg_accepted(&req.req) {
                continue;
            }
            let id = license_string(&req.req);
            license_names.entry(id.clone()).or_insert_with(|| license_full_name(&req.req));
            used_ids.insert(id);
        }

        // The `authors` field is optional and newer crates increasingly omit
        // it; salvage the copyright holder(s) from the license files shipped

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