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@@ -- Add Express V4 Support to @salesforce/mrt-utilities package. #334

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Merged
bendvc merged 6 commits into from
Apr 10, 2026
Merged

@@ -- Add Express V4 Support to @salesforce/mrt-utilities package. #334

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c09aa66
Initial Commit
bendvc Apr 10, 2026
c00eddb
Update CHANGELOG.md
bendvc Apr 10, 2026
7cfe512
Change peer to have a wider support range for 4.x
bendvc Apr 10, 2026
ac18a77
Revert manual changelog update; replace with changeset
bendvc Apr 10, 2026
2545889
Add some docs to better understand this pattern
bendvc Apr 10, 2026
ebcdd6d
No monkey patching
bendvc Apr 10, 2026
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5 changes: 5 additions & 0 deletions .changeset/mrt-utilities-express-4-support.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
'@salesforce/mrt-utilities': patch
---

Add Express 4 support, improve middleware error handling, and add dual-version Express test coverage.
3 changes: 2 additions & 1 deletion packages/mrt-utilities/package.json
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Expand Up @@ -115,6 +115,7 @@
"eslint-plugin-header": "catalog:",
"eslint-plugin-prettier": "catalog:",
"express": "5.1.0",
"express4": "npm:express@4.21.2",
"mocha": "catalog:",
"prettier": "catalog:",
"shx": "catalog:",
Expand All @@ -124,7 +125,7 @@
"typescript-eslint": "catalog:"
},
"peerDependencies": {
"express": "5.1.0"
"express": "^4.0.0 || ^5.0.0"
},
"engines": {
"node": ">=22.16.0"
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28 changes: 16 additions & 12 deletions packages/mrt-utilities/src/middleware/middleware.ts
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Expand Up @@ -272,7 +272,7 @@ export const createMRTRequestProcessorMiddleware = (
req.headers[X_MOBIFY_REQUEST_PROCESSOR_LOCAL] = 'true'; // Mark the request as processed by the request processor
};

const ssrRequestProcessorMiddleware = async (req: Request, res: Response, next: NextFunction) => {
const ssrRequestProcessorMiddleware = (req: Request, res: Response, next: NextFunction) => {
// If the path is /, we enforce that the only methods
// allowed are GET, HEAD or OPTIONS. This is a restriction
// imposed by API Gateway: we enforce it here so that the
Expand All @@ -282,17 +282,21 @@ export const createMRTRequestProcessorMiddleware = (
return;
}

// Apply custom query parameter parsing.
await processIncomingRequest(req, res);

// Strip out API Gateway headers from the incoming request. We
// do that now so that the rest of the code don't have to deal
// with these headers, which can be large and may be accidentally
// forwarded to other servers.
cleanUpHeaders(req, false);

// Hand off to the next middleware
next();
// Apply custom query parameter parsing and forward errors via next()
processIncomingRequest(req, res)
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@kieran-sf kieran-sf Apr 10, 2026

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Can you explain the reason for the change here, I am just curious

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@bendvc bendvc Apr 10, 2026

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We made that change so this middleware works in Express 4.
Express 4 doesn’t always handle async errors, so we now call processIncomingRequest(...) and only call next() after it finishes, and if it fails we pass the error to next(err). This keeps the same behaviour but avoids unhandled promise errors. The function signature isn't changed, so we don't have a breaking change.

.then(() => {
// Strip out API Gateway headers from the incoming request. We
// do that now so that the rest of the code don't have to deal
// with these headers, which can be large and may be accidentally
// forwarded to other servers.
cleanUpHeaders(req, false);

// Hand off to the next middleware
next();
})
.catch((err) => {
next(err);
});
};

return ssrRequestProcessorMiddleware;
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23 changes: 23 additions & 0 deletions packages/mrt-utilities/test/helpers/express-versions.ts
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/*
* Copyright (c) 2025, Salesforce, Inc.
* SPDX-License-Identifier: Apache-2
* For full license text, see the license.txt file in the repo root or http://www.apache.org/licenses/LICENSE-2.0
*/

import express5 from 'express';
import {createRequire} from 'node:module';

/*
* Load Express v4 via an npm alias so tests can run against v4 and v5
* in the same process without altering production imports.
*/
const require = createRequire(import.meta.url);
const express4 = require('express4') as typeof express5;

/*
* Export both versions for parameterized test suites.
*/
export const expressVersions = [
{label: 'express4', express: express4},
{label: 'express5', express: express5},
];
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