fix: handle long text values performantly (#1874)

* test: add test for long text performance

This test fails in the current state, as jsondiffpatch
uses the diff-match-patch library for long text diffing.
This text diff is very slow, but produces a nice delta that
can be used to see the difference between two text strings.
However, we don't actually care about identifying the specific
differences between two strings - we just care if they changed.
The regular text diffing strategy is MUCH faster, and performance
is what we want to prioritize.

- https://github.com/benjamine/jsondiffpatch/blob/master/docs/deltas.md#text-diffs
- https://github.com/google/diff-match-patch

* fix: disable diff-match-patch for long string diff

jsondiffpatch uses diff-match-patch for long text diffing.
This text diff is very slow, but produces a nice delta that
can be used to see the difference between two text strings.
However, we don't actually care about identifying the specific
differences between two strings - we just care if they changed.
The regular text diffing strategy is MUCH faster, and performance
is what we want to prioritize.

- https://github.com/benjamine/jsondiffpatch/blob/master/docs/deltas.md#text-diffs
- https://github.com/google/diff-match-patch

* docs: add changeset

---------

Co-authored-by: Markus Azer <markusgihady@gmail.com>

Author: taylor-knapp

.changeset/violet-timers-act.md

@@ -0,0 +1,5 @@
+---
+'@commercetools/sync-actions': minor
+---
+
+Handle long text values performantly

packages/sync-actions/src/utils/diffpatcher.js

@@ -20,11 +20,14 @@ const diffpatcher = new DiffPatcher({
     includeValueOnMove: false,
   },
   textDiff: {
-    // If the value to diff has a bigger length,
-    // a text diffing algorithm is used
-    // See https://github.com/benjamine/jsondiffpatch/
-    // blob/master/docs/deltas.md#text-diffs
-    minLength: 300,
+    /**
+     * jsondiffpatch uses a very fine-grained diffing algorithm for long strings to easily identify
+     * what changed between strings. However, we don't actually care about what changed, just
+     * if the string changed at all. So we set the minimum length to diff to a very large number to avoid
+     * using the very slow algorithm.
+     * See https://github.com/benjamine/jsondiffpatch/blob/master/docs/deltas.md#text-diffs.
+     */
+    minLength: Number.MAX_SAFE_INTEGER,
   },
 })
 

packages/sync-actions/test/product-sync-variants.spec.js

@@ -116,6 +116,78 @@ describe('Actions', () => {
     ])
   })
 
+  test('should handle long text values performantly', () => {
+    const longText = 'a'.repeat(10_000)
+    const longText2 = 'b'.repeat(10_000)
+    const before = {
+      id: '123',
+      masterVariant: {
+        id: 1,
+        attributes: [
+          { name: 'color', value: longText },
+          { name: 'size', value: longText },
+          { name: 'weight', value: longText },
+        ],
+      },
+      variants: [
+        {
+          id: 2,
+          attributes: [
+            { name: 'color', value: longText },
+            { name: 'size', value: longText },
+            { name: 'weight', value: longText },
+          ],
+        },
+      ],
+    }
+
+    const now = {
+      id: '123',
+      masterVariant: {
+        id: 1,
+        attributes: [
+          { name: 'color', value: longText2 },
+          { name: 'size', value: longText2 },
+          { name: 'weight', value: longText2 },
+        ],
+      },
+      variants: [
+        {
+          id: 2,
+          attributes: [
+            { name: 'color', value: longText2 },
+            { name: 'size', value: longText2 },
+            { name: 'weight', value: longText2 },
+          ],
+        },
+      ],
+    }
+
+    const startTime = Date.now()
+    const actions = productsSync.buildActions(now, before)
+
+    // Should take less than 100ms.
+    expect(Date.now() - startTime).toBeLessThan(100)
+    expect(actions).toEqual([
+      { action: 'setAttribute', variantId: 1, name: 'color', value: longText2 },
+      { action: 'setAttribute', variantId: 1, name: 'size', value: longText2 },
+      {
+        action: 'setAttribute',
+        variantId: 1,
+        name: 'weight',
+        value: longText2,
+      },
+      { action: 'setAttribute', variantId: 2, name: 'color', value: longText2 },
+      { action: 'setAttribute', variantId: 2, name: 'size', value: longText2 },
+      {
+        action: 'setAttribute',
+        variantId: 2,
+        name: 'weight',
+        value: longText2,
+      },
+    ])
+  })
+
   test('should build SameForAll attribute actions', () => {
     const before = {
       id: '123',