property metafile | Bun module | Bun

Metadata about the build including inputs, outputs, and their relationships.

Only present when BuildConfig.metafile is true.

The metafile contains detailed information about:

This can be used for:

const result = await Bun.build({
entrypoints: ['./src/index.ts'],
outdir: './dist',
metafile: true,
});

if (result.metafile) {
// Analyze input files
for (const [path, input] of Object.entries(result.metafile.inputs)) {
console.log(`${path}: ${input.bytes} bytes, ${input.imports.length} imports`);
}

// Analyze output files
for (const [path, output] of Object.entries(result.metafile.outputs)) {
console.log(`${path}: ${output.bytes} bytes`);
for (const [inputPath, info] of Object.entries(output.inputs)) {
console.log(` - ${inputPath}: ${info.bytesInOutput} bytes`);
}
}

// Write to disk for external analysis tools
await Bun.write('./dist/meta.json', JSON.stringify(result.metafile));
}