slint-ui/slint · error · CompileError

Could not compile ${filePath}

Error message

Could not compile ${filePath}

What it means

The Node.js slint API (loadFile/loadSource in api/node/typescript/index.ts) compiles .slint markup at runtime through the native ComponentCompiler. After buildFromPath/buildFromSource, it filters the compiler diagnostics; if any diagnostic has level Error, it throws a CompileError whose message is 'Could not compile <filePath>' plus a formatted list of every diagnostic (file:line:column + message). The raw napi.Diagnostic array stays available on error.diagnostics.

Source

Thrown at api/node/typescript/index.ts:340

            ? compiler.buildFromPath(filePath)
            : compiler.buildFromSource(loadData.fileData.source, filePath);
    const diagnostics = compiler.diagnostics;

    if (diagnostics.length > 0) {
        const warnings = diagnostics.filter(
            (d) => d.level === napi.DiagnosticLevel.Warning,
        );

        if (typeof options !== "undefined" && options.quiet !== true) {
            warnings.forEach((w) => console.warn("Warning: " + w));
        }

        const errors = diagnostics.filter(
            (d) => d.level === napi.DiagnosticLevel.Error,
        );

        if (errors.length > 0) {
            throw new CompileError("Could not compile " + filePath, errors);
        }
    }

    const slint_module = Object.create({});

    // generate structs
    const structs = compiler.structs;

    for (const key in compiler.structs) {
        Object.defineProperty(slint_module, translateName(key), {
            value: function (properties: any) {
                const defaultObject = structs[key] as any;
                const newObject = Object.create({});

                for (const propertyKey in defaultObject) {
                    const propertyName = translateName(propertyKey);
                    const propertyValue =
                        properties !== undefined &&

View on GitHub (pinned to a9ea814a58)

Solutions

1. Catch the CompileError and read error.diagnostics (fileName, lineNumber, columnNumber, message) to locate each problem in the markup.
2. Fix the reported .slint location(s): spelling of elements/properties, property value types, or missing imports.
3. If imports fail, pass correct includePaths (and libraryPaths for @library imports) in the LoadFileOptions argument.
4. Pre-check the file outside Node with `cargo run --bin slint-viewer -- app.slint` or the Slint LSP/VS Code extension.
5. Pin the slint-ui npm version that matches the .slint feature set you use.

Example fix

// before
import { loadFile } from "slint-ui";
const ui = loadFile("app.slint"); // throws: Could not compile app.slint

// after
import { loadFile, CompileError } from "slint-ui";
try {
    const ui = loadFile("app.slint");
} catch (e) {
    if (e instanceof CompileError) {
        for (const d of e.diagnostics) {
            console.error(`[${d.fileName}:${d.lineNumber}:${d.columnNumber}] ${d.message}`);
        }
        process.exit(1);
    }
    throw e;
}

function isCompileError(e: unknown): e is import("slint-ui").CompileError {
    return e instanceof Error && (e as any).diagnostics !== undefined;
}

try {
    const ui = loadFile("app.slint");
} catch (e) {
    if (e instanceof CompileError) {
        for (const d of e.diagnostics) console.error(`${d.fileName}:${d.lineNumber}:${d.columnNumber}: ${d.message}`);
        process.exitCode = 1;
    } else throw e;
}

When it happens

Trigger: Calling loadFile("app.slint") or loadSource(source, filePath) with markup that fails to compile: syntax errors, unknown elements or properties, wrong property types, unresolved `import { X } from "..."` files, or referencing widgets from a style that is not set via the style option.

Common situations: Typos in element/property names in .slint; imports of files not covered by the includePaths option; upgrading slint-ui to a version that renamed or removed properties; CI running with a different widget style default; passing a wrong absolute/relative path so imported files cannot be found.

Related errors

• Could not compile {path}
• slint-ui-dev must not be imported directly — it only provide
• Callback '{name}' in global '{global_name}' cannot be used w
• Callback '{name}' in global '{global_name}' cannot be used w
• Callback '{name}' cannot be used with a callback decorator f

AI-assisted analysis of slint-ui/slint@a9ea814a58 (2026-08-16). Data as JSON: /api/errors/b57793ec266142a6. Report an issue: GitHub.