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feat: improved text splitter #5539

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fea5741
feat: text splitter
samdenty Apr 3, 2025
00d483d
chore: add changeset
samdenty Apr 3, 2025
08fd40c
Merge remote-tracking branch 'origin/main' into feat/smooth-stream-cjk
samdenty Apr 3, 2025
6c06aae
chore: add comment
samdenty Apr 3, 2025
5a6be5d
chore: review
samdenty Apr 3, 2025
9555705
fix
samdenty Apr 3, 2025
61d57db
fix: lint
samdenty Apr 3, 2025
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5 changes: 5 additions & 0 deletions .changeset/beige-seals-tie.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
'ai': patch
---

feat(ai): improved text splitter
140 changes: 133 additions & 7 deletions packages/ai/core/generate-text/smooth-stream.test.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -46,6 +46,7 @@ describe('smoothStream', () => {
textDelta: 'Hello, ',
type: 'text-delta',
},
'delay 10',
{
textDelta: 'world!',
type: 'text-delta',
Expand Down Expand Up @@ -107,6 +108,7 @@ describe('smoothStream', () => {
textDelta: 'example ',
type: 'text-delta',
},
'delay 10',
{
textDelta: 'text.',
type: 'text-delta',
Expand Down Expand Up @@ -146,21 +148,22 @@ describe('smoothStream', () => {
},
'delay 10',
{
textDelta: 'line \n\n',
textDelta: 'line \n\n ',
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@lgrammel lgrammel Apr 3, 2025

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this will create an additional delay

type: 'text-delta',
},
'delay 10',
{
// note: leading whitespace is included here
// because it is part of the new chunk:
textDelta: ' Multiple ',
// note: leading whitespace not included here
// because it is part of the last chunk:
textDelta: 'Multiple ',
type: 'text-delta',
},
'delay 10',
{
textDelta: 'spaces\n ',
type: 'text-delta',
},
'delay 10',
{
textDelta: 'Indented',
type: 'text-delta',
Expand Down Expand Up @@ -223,6 +226,7 @@ describe('smoothStream', () => {
"textDelta": "in ",
"type": "text-delta",
},
"delay 10",
{
"textDelta": "London.",
"type": "text-delta",
Expand Down Expand Up @@ -299,6 +303,7 @@ describe('smoothStream', () => {
"textDelta": "in ",
"type": "text-delta",
},
"delay 10",
{
"textDelta": "London.",
"type": "text-delta",
Expand Down Expand Up @@ -333,6 +338,127 @@ describe('smoothStream', () => {
]
`);
});

it('should support kanji', async () => {
const stream = convertArrayToReadableStream([
{ textDelta: 'Vercel', type: 'text-delta' },
{ textDelta: 'はサ', type: 'text-delta' },
{ textDelta: 'サーバーレス', type: 'text-delta' },
{ textDelta: 'の', type: 'text-delta' },
{ textDelta: 'フロントエンド', type: 'text-delta' },
{ textDelta: 'Hello, world!', type: 'text-delta' },
{ type: 'step-finish' },
{ type: 'finish' },
]).pipeThrough(
smoothStream({
delayInMs: 10,
_internal: { delay },
})({ tools: {} }),
);

await consumeStream(stream);

expect(events).toMatchInlineSnapshot(`
[
"delay 10",
{
"textDelta": "Vercelは",
"type": "text-delta",
},
"delay 10",
{
"textDelta": "サ",
"type": "text-delta",
},
"delay 10",
{
"textDelta": "サ",
"type": "text-delta",
},
"delay 10",
{
"textDelta": "ー",
"type": "text-delta",
},
"delay 10",
{
"textDelta": "バ",
"type": "text-delta",
},
"delay 10",
{
"textDelta": "ー",
"type": "text-delta",
},
"delay 10",
{
"textDelta": "レ",
"type": "text-delta",
},
"delay 10",
{
"textDelta": "ス",
"type": "text-delta",
},
"delay 10",
{
"textDelta": "の",
"type": "text-delta",
},
"delay 10",
{
"textDelta": "フ",
"type": "text-delta",
},
"delay 10",
{
"textDelta": "ロ",
"type": "text-delta",
},
"delay 10",
{
"textDelta": "ン",
"type": "text-delta",
},
"delay 10",
{
"textDelta": "ト",
"type": "text-delta",
},
"delay 10",
{
"textDelta": "エ",
"type": "text-delta",
},
"delay 10",
{
"textDelta": "ン",
"type": "text-delta",
},
"delay 10",
{
"textDelta": "ド",
"type": "text-delta",
},
"delay 10",
{
"textDelta": "Hello, ",
"type": "text-delta",
},
"delay 10",
{
"textDelta": "world!",
"type": "text-delta",
},
{
"type": "step-finish",
},
{
"type": "finish",
},
]
`);
});
});

describe('line chunking', () => {
Expand Down Expand Up @@ -450,9 +576,7 @@ describe('smoothStream', () => {
'delay 10',
{ textDelta: 'o', type: 'text-delta' },
'delay 10',
{ textDelta: ',', type: 'text-delta' },
'delay 10',
{ textDelta: ' ', type: 'text-delta' },
{ textDelta: ', ', type: 'text-delta' },
'delay 10',
{ textDelta: 'w', type: 'text-delta' },
'delay 10',
Expand Down Expand Up @@ -491,6 +615,7 @@ describe('smoothStream', () => {
textDelta: 'Hello, ',
type: 'text-delta',
},
'delay 10',
{
textDelta: 'world!',
type: 'text-delta',
Expand Down Expand Up @@ -524,6 +649,7 @@ describe('smoothStream', () => {
textDelta: 'Hello, ',
type: 'text-delta',
},
'delay 20',
{
textDelta: 'world!',
type: 'text-delta',
Expand Down
56 changes: 42 additions & 14 deletions packages/ai/core/generate-text/smooth-stream.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -2,10 +2,12 @@ import { InvalidArgumentError } from '@ai-sdk/provider';
import { delay as originalDelay } from '@ai-sdk/provider-utils';
import { TextStreamPart } from './stream-text-result';
import { ToolSet } from './tool-set';
import { TextSplit, splitText } from './text-splitter';

const CHUNKING_REGEXPS = {
word: /\s*\S+\s+/m,
line: /[^\n]*\n/m,
character: /(?!\s)(?=.)/g,
word: /[\u4E00-\u9FFF\u3040-\u309F\u30A0-\u30FF]|\s+/gm,
line: /\r\n|\r|\n/g,
Comment on lines +8 to +10
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@lgrammel lgrammel Apr 3, 2025

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what will happen to custom user regexp?

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@samdenty samdenty Apr 3, 2025

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i'll add more tests for custom chunking

};

/**
Expand All @@ -22,7 +24,7 @@ export function smoothStream<TOOLS extends ToolSet>({
_internal: { delay = originalDelay } = {},
}: {
delayInMs?: number | null;
chunking?: 'word' | 'line' | RegExp;
chunking?: 'character' | 'word' | 'line' | { split: string } | RegExp;
/**
* Internal. For test use only. May change without notice.
*/
Expand All @@ -32,10 +34,14 @@ export function smoothStream<TOOLS extends ToolSet>({
} = {}): (options: {
tools: TOOLS;
}) => TransformStream<TextStreamPart<TOOLS>, TextStreamPart<TOOLS>> {
const chunkingRegexp =
typeof chunking === 'string' ? CHUNKING_REGEXPS[chunking] : chunking;
const chunker =
typeof chunking === 'object' && 'split' in chunking
? chunking.split
: typeof chunking === 'string'
? CHUNKING_REGEXPS[chunking]
: chunking;

if (chunkingRegexp == null) {
if (chunker == null) {
throw new InvalidArgumentError({
argument: 'chunking',
message: `Chunking must be "word" or "line" or a RegExp. Received: ${chunking}`,
Expand All @@ -44,12 +50,24 @@ export function smoothStream<TOOLS extends ToolSet>({

return () => {
let buffer = '';
let lastSplits: TextSplit[] = [];
let lastIndex = 0;

return new TransformStream<TextStreamPart<TOOLS>, TextStreamPart<TOOLS>>({
async transform(chunk, controller) {
const lastSplit = lastSplits.at(-1);

if (chunk.type !== 'text-delta') {
if (buffer.length > 0) {
controller.enqueue({ type: 'text-delta', textDelta: buffer });
if (lastSplits.length > 1 && delayInMs) {
await delay(delayInMs);
}

if (lastSplit) {
controller.enqueue({
type: 'text-delta',
textDelta: lastSplit.text,
});
lastSplits = [];
buffer = '';
}

Expand All @@ -59,14 +77,24 @@ export function smoothStream<TOOLS extends ToolSet>({

buffer += chunk.textDelta;

let match;
while ((match = chunkingRegexp.exec(buffer)) != null) {
const chunk = match[0];
controller.enqueue({ type: 'text-delta', textDelta: chunk });
buffer = buffer.slice(chunk.length);
const splits = splitText(buffer, chunker);

await delay(delayInMs);
// If there's a new split with the start index greater than the last index,
// push the new split(s) and delay.
const newSplitIndex = splits.findIndex(
split => !lastSplit || split.start >= lastIndex,
);

if (newSplitIndex !== -1) {
for (let i = newSplitIndex; i < splits.length - 1; i++) {
const split = splits[i];
controller.enqueue({ type: 'text-delta', textDelta: split.text });
lastIndex = split.end;
await delay(delayInMs);
}
}

lastSplits = splits;
},
});
};
Expand Down
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