Add support for escape characters

[thomas-lcdp]

Description
In Algolia we can exclude values by adding an escape character "-" as explain in documentation
https://www.algolia.com/doc/api-reference/api-parameters/facetFilters/#escape-characters

Solution
Maybe add the conversion from attribute=-value to attribute!=value in file-adapter.ts

/**
 * Transform InstantSearch [facet filter](https://www.algolia.com/doc/api-reference/api-parameters/facetFilters/)
 * to Meilisearch compatible filter format.
 * Change sign from `:` to `=`
 * "facet:facetValue" becomes "facet=facetValue"
 *
 * Wrap both the facet and its facet value between quotes.
 * This avoids formatting issues on facets containing multiple words.
 * Escape backslash \\ and quote " characters.
 *
 * 'My facet:My facet value' becomes '"My facet":"My facet value"'
 *
 * @param {string} filter
 * @returns {string}
 */
function transformFacetFilter(filter: string): string {
  const escapedFilter = getValueWithEscapedBackslashesAndQuotes(filter)
  const colonIndex = escapedFilter.indexOf(':')
  const attribute = escapedFilter.slice(0, colonIndex)
  const value = escapedFilter.slice(colonIndex + 1)
  return `"${attribute}"="${value}"`
}

[curquiza]

Hello @thomas-lcdp

Thank you for the suggestion

I'm not sure it will work (or maybe I did not understand) because meilisearch, the search engine itself, is not able to accept escaped value.
I tried to create a facet field named -price and then to apply facet search on it , but the engine does not return anything

/indexes/{{indexUID}}/facet-search
{ 
      "facetName": "-price",
      "q": ""
}

{
    "facetHits": [],
    "facetQuery": null,
    "processingTimeMs": 0
}

I think it's more a bug on the engine side, what do you think?

[thomas-lcdp]

Hello @curquiza

In Algolia, the escaped value is supported, so you can have a facetFilters: ["owner.id:-7"] to exclude data.
But the conversion from meilisearch-instantsearch is owner.id = -7
Maybe it could be possible to transform owner.id:-7 to owner.id != 7

[curquiza]

Oh, in my previous message I confused with "search in facet value". We don't always have the same naming with Algolia.

I think I now better understand your issue. When you want to do filter, you want Meilisearch to send "filter": "\"field\" = \"my value\"" instead of "filter": "field = my value"?

Specifically, regarding what you said about the -: the search engine itself does not support the exclusion of some facets value or filter with - but with the NOT