Remove webpack stats generation from Turbopack - #91515
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The TURBOPACK_STATS feature generated webpack-compatible stats.json files from Turbopack's output, but it is no longer needed. Remove the entire feature: the Rust implementation (webpack_stats.rs), all call sites in app.rs and pages.rs, the project flag, and all TypeScript manifest loading, merging, and writing code. Co-Authored-By: Claude <noreply@anthropic.com>
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Merging this PR will degrade performance by 3.99%
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wbinnssmith
approved these changes
Mar 17, 2026
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What?
Remove the
TURBOPACK_STATSfeature that generated webpack-compatiblewebpack-stats.jsonfiles from Turbopack's output.Deleted:
crates/next-api/src/webpack_stats.rs— the entire 305-line Rust implementation that built webpack-format stats (assets, chunks, modules, entrypoints) from Turbopack's module graphRust changes:
crates/next-api/src/lib.rs— removedmod webpack_stats;crates/next-api/src/project.rs— removedshould_create_webpack_stats()which read theTURBOPACK_STATSenv varcrates/next-api/src/pages.rs— removedgenerate_webpack_statsimport and stats output emissioncrates/next-api/src/app.rs— sameTypeScript changes:
packages/next/src/shared/lib/constants.ts— removedWEBPACK_STATS = 'webpack-stats.json'constantpackages/next/src/shared/lib/turbopack/manifest-loader.ts— removedloadWebpackStats(),writeWebpackStats(),mergeWebpackStats(), thewebpackStatsfield, webpack type imports, and theTURBOPACK_STATSenv guard inwriteManifests()packages/next/src/server/dev/turbopack-utils.ts— removedshouldCreateWebpackStatsflag and twoloadWebpackStats()call sitespackages/next/src/build/handle-entrypoints.ts— sameWhy?
This feature is no longer needed and adds dead complexity. It was opt-in via
TURBOPACK_STATS=1but nothing in the current codebase or tooling depends on it.How?
Pure deletion — no behavior change for any existing user, as the feature was opt-in via an environment variable that is no longer checked.
Intentionally left untouched:
stats.jsongeneration (non-Turbopack path)analyzefeatureroute-bundle-stats.jsonin.next/diagnostics/