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Default add_prefix_space=true for metaspace pretokenizer #1451

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Merged
merged 3 commits into from
Nov 10, 2025
Merged

Default add_prefix_space=true for metaspace pretokenizer #1451

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b33281a
Default add_prefix_space=true for metaspace pretokenizer
xenova Nov 10, 2025
79a83d1
Remove metaspace add_prefix_space logic (pre_tokenizer + decoder)
xenova Nov 10, 2025
e6e5f50
Fix bad test!
xenova Nov 10, 2025
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12 changes: 3 additions & 9 deletions src/tokenizers.js
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Original file line number Diff line number Diff line change
Expand Up @@ -2279,15 +2279,13 @@ class VitsDecoder extends Decoder {
class MetaspacePreTokenizer extends PreTokenizer {
/**
* @param {Object} config The configuration object for the MetaspacePreTokenizer.
* @param {boolean} config.add_prefix_space Whether to add a prefix space to the first token.
* @param {string} config.replacement The character to replace spaces with.
* @param {string} [config.str_rep=config.replacement] An optional string representation of the replacement character.
* @param {'first'|'never'|'always'} [config.prepend_scheme='always'] The metaspace prepending scheme.
*/
constructor(config) {
super();

this.addPrefixSpace = config.add_prefix_space;
this.replacement = config.replacement;
this.strRep = config.str_rep || this.replacement;
this.prepend_scheme = config.prepend_scheme ?? 'always';
Expand All @@ -2309,9 +2307,8 @@ class MetaspacePreTokenizer extends PreTokenizer {

if (
// We add a prefix space if:
// (1) The addPrefixSpace option is enabled and the normalized
// token does not already start with the replacement character.
(this.addPrefixSpace && !normalized.startsWith(this.replacement))
// (1) The normalized token does not already start with the replacement character.
!normalized.startsWith(this.replacement)

// and (2) either:
// (a) prepend_scheme is 'always'
Expand All @@ -2335,13 +2332,11 @@ class MetaspaceDecoder extends Decoder {
/**
* Constructs a new MetaspaceDecoder object.
* @param {Object} config The configuration object for the MetaspaceDecoder.
* @param {boolean} config.add_prefix_space Whether to add a prefix space to the decoded string.
* @param {string} config.replacement The string to replace spaces with.
*/
constructor(config) {
super(config);

this.addPrefixSpace = config.add_prefix_space;
this.replacement = config.replacement;
}

Expand All @@ -2350,7 +2345,7 @@ class MetaspaceDecoder extends Decoder {
const result = [];
for (let i = 0; i < tokens.length; ++i) {
let normalized = tokens[i].replaceAll(this.replacement, ' ');
if (this.addPrefixSpace && i == 0 && normalized.startsWith(' ')) {
if (i == 0 && normalized.startsWith(' ')) {
normalized = normalized.substring(1);
}
result.push(normalized);
Expand Down Expand Up @@ -3425,7 +3420,6 @@ export class LlamaTokenizer extends PreTrainedTokenizer {
this.normalizer = null;
this.pre_tokenizer = new MetaspacePreTokenizer({
replacement: SPIECE_UNDERLINE,
add_prefix_space: true,
prepend_scheme: "first",
});
}
Expand Down
4 changes: 2 additions & 2 deletions tests/models/jina_clip/test_processor_jina_clip.js
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Expand Up @@ -33,8 +33,8 @@ export default () => {
// Encode text and images
const { input_ids, attention_mask, pixel_values } = await processor(sentences, images, { padding: true, truncation: true });

expect(input_ids.dims).toEqual([sentences.length, 19]);
expect(attention_mask.dims).toEqual([sentences.length, 19]);
expect(input_ids.dims).toEqual([sentences.length, 14]);
expect(attention_mask.dims).toEqual([sentences.length, 14]);
expect(pixel_values.dims).toEqual([images.length, 3, 512, 512]);
expect(pixel_values.mean().item()).toBeCloseTo(0.7857685685157776, 6);
},
Expand Down