fix trailing comma causing unncessary diffs

Author: emily-shen

packages/wrangler/src/__tests__/containers/deploy.test.ts

@@ -716,8 +716,6 @@ describe("wrangler deploy with containers", () => {
 				│   {
 				│   ...
 				│   \\"image\\": \\"docker.io/hello:world\\",
-				│ - \\"instance_type\\": \\"dev\\"
-				│ + \\"instance_type\\": \\"dev\\",
 				│ + \\"observability\\": {
 				│ + \\"logs\\": {
 				│ + \\"enabled\\": true
@@ -762,8 +760,6 @@ describe("wrangler deploy with containers", () => {
 				│   {
 				│   ...
 				│   \\"image\\": \\"docker.io/hello:world\\",
-				│ - \\"instance_type\\": \\"dev\\"
-				│ + \\"instance_type\\": \\"dev\\",
 				│ + \\"observability\\": {
 				│ + \\"logs\\": {
 				│ + \\"enabled\\": true

packages/wrangler/src/cloudchamber/helpers/diff.ts

@@ -561,3 +561,30 @@ export const renderDiff = (results: Result[]) => {
 		}
 	}
 };
+
+/**
+ * Filter out trailing comma differences that are just formatting changes.
+ * This prevents showing spurious diffs when JSON properties get trailing commas
+ * added/removed due to new properties being inserted.
+ */
+export function filterTrailingCommaChanges(results: Result[]): Result[] {
+	// First, identify pairs of removed/added lines that are just comma changes
+	const commaChangePairs = new Set<Result>();
+	
+	results.forEach((result) => {
+		if (result.removed && result.value) {
+			// Look for a corresponding added line that's the same but with comma
+			const potentialMatch = results.find((r) => 
+				r.added && r.value === result.value + ','
+			);
+			if (potentialMatch) {
+				// This is a trailing comma change, mark both for filtering
+				commaChangePairs.add(result);
+				commaChangePairs.add(potentialMatch);
+			}
+		}
+	});
+	
+	// Filter out the identified comma change pairs
+	return results.filter((result) => !commaChangePairs.has(result));
+}

packages/wrangler/src/containers/deploy.ts

@@ -23,6 +23,7 @@ import {
 import { inferInstanceType, promiseSpinner } from "../cloudchamber/common";
 import {
 	diffLines,
+	filterTrailingCommaChanges,
 	printLine,
 	renderDiff,
 	sortObjectRecursive,
@@ -312,7 +313,8 @@ export async function apply(
 		const prev = JSON.stringify({ containers: [normalisedPrevApp] }, null, 2);
 		const now = JSON.stringify({ containers: [nowContainer] }, null, 2);
 
-		const results = diffLines(prev, now);
+		const rawResults = diffLines(prev, now);
+		const results = filterTrailingCommaChanges(rawResults);
 		const changes = results.find((l) => l.added || l.removed) !== undefined;
 
 		if (!changes) {