Eexpressjs

expressjs/static-mime

Migrates express.static.mime (removed in Express 5) to the mime-types package

transformationmigrationexpressstaticmimemime-typesexpress.static.mime
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Migrate express.static.mime

In Express 5, mime is no longer an exported property of express.static. The
mime-types package should be used to
work with MIME type values instead.

This codemod rewrites every express.static.mime reference to use a mime-types
binding and adds the corresponding import/require to the file:

  1. Replaces express.static.mime with a mime-types local binding (default name mime).
  2. Adds the import once per file, matching how express is imported
    (import mime from 'mime-types' for ESM, const mime = require('mime-types') for CommonJS).
  3. Reuses an existing mime-types import when the file already has one, and falls
    back to a non-colliding name (mimeTypes) when mime is already taken.

The object Express 4 exposed as express.static.mime was a mime@1.x
instance, whose API is not identical to mime-types. The codemod rewrites
each member accordingly:

express.static.mime (mime@1.x)mime-typesHandled by
.lookup(path).lookup(path)rename of the binding
.extension(type).extension(type)rename of the binding
.types / .extensions.types / .extensionsrename of the binding
.charsets.lookup(type).charset(type)method rewrite
.define(map)no equivalentflagged with a TODO comment
.load(path)no equivalentflagged with a TODO comment
.default_typeno equivalentflagged with a TODO comment

Example

diff

Renamed method

diff

Methods without a mime-types equivalent

define, load, and default_type cannot be migrated automatically, so the
codemod points them at the new binding and flags them for manual review:

diff

CommonJS

diff

package.json

For projects that depend on express, the codemod also adds mime-types to the
same dependency section, so the newly referenced package is declared:

diff

An existing mime-types entry is left untouched, and package.json files without
express are not modified.

Notes

  • Behavior differs slightly even for the shared methods: mime-types returns
    false for unknown input, whereas mime@1.x lookup() fell back to
    default_type (application/octet-stream). Review code that relied on that
    fallback.
  • Members flagged with a TODO comment (define, load, default_type) have no
    mime-types equivalent and must be migrated by hand.
  • Run npm install after the migration so the added mime-types dependency is installed.

References

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