Support indexing arrays of strings

CHANGELOG.md

@@ -6,6 +6,7 @@
 * [#57](https://github.com/mongoid/mongoid_fulltext/pull/57): Respect criteria and single-collection inheritance, skip dangling references, and apply result limits after filtering - [@tomasc](https://github.com/tomasc), [@dblock](https://github.com/dblock).
 * [#56](https://github.com/mongoid/mongoid_fulltext/pull/56): Support Unicode-aware regular expressions for alphabets without enumerating characters - [@dblock](https://github.com/dblock).
 * [#54](https://github.com/mongoid/mongoid_fulltext/pull/54): Insert ngrams in a batch per document index and continue past empty indexes - [@dblock](https://github.com/dblock).
+* [#53](https://github.com/mongoid/mongoid_fulltext/pull/53): Support indexing array fields containing strings - [@dblock](https://github.com/dblock).
 * [#51](https://github.com/mongoid/mongoid_fulltext/pull/51): Modernize CI through Ruby 4.0, Mongoid 9, and MongoDB 8 with real coverage, RuboCop 1.92, and fork-safe Danger workflows - [@dblock](https://github.com/dblock).
 * [#45](https://github.com/mongoid/mongoid_fulltext/pull/45): Allow for class level ngram updates to not timeout - [@roykolak](https://github.com/roykolak).
 * Your contribution here.

README.md

@@ -67,6 +67,8 @@ class Artist
 end
 ```
 
+Array fields containing strings are supported alongside scalar fields, for example `fulltext_search_in :title, :tags` with `field :tags, type: Array`. Each array element is indexed independently, so ngrams do not span tags. Nil and empty elements are ignored; changing or clearing the array replaces its old index entries.
+
 To restrict the number of results returned, pass the `:max_results` parameter to `fulltext_search`:
 
 ``` ruby

lib/mongoid/full_text_search.rb

@@ -386,7 +386,7 @@ def update_ngram_index
         coll.find(removal_query).remove_all
       end
       # extract ngrams from fields
-      field_values = fulltext_config[:ngram_fields].map { |field| send(field) }
+      field_values = fulltext_config[:ngram_fields].flat_map { |field| send(field) }
       ngrams = field_values.inject({}) { |accum, item| accum.update(self.class.all_ngrams(item, fulltext_config, false)) }
       next if ngrams.empty?
 

spec/models/tagged_artwork.rb

@@ -0,0 +1,9 @@
+class TaggedArtwork
+  include Mongoid::Document
+  include Mongoid::FullTextSearch
+
+  field :title, type: String
+  field :tags, type: Array
+
+  fulltext_search_in :title, :tags
+end

spec/mongoid/array_fields_spec.rb

@@ -0,0 +1,43 @@
+require 'spec_helper'
+
+describe 'Array fields' do
+  it 'searches each tag as well as scalar fields' do
+    artwork = TaggedArtwork.create!(title: 'Painting', tags: %w[ghost accounting])
+    %w[painting ghost accounting].each do |query|
+      expect(TaggedArtwork.fulltext_search(query)).to eq([artwork])
+    end
+  end
+
+  it 'does not create ngrams across array element boundaries' do
+    artwork = TaggedArtwork.create!(tags: %w[ab cd])
+    config = TaggedArtwork.mongoid_fulltext_config.values.first
+    coll = artwork.collection.database[TaggedArtwork.mongoid_fulltext_config.keys.first]
+    expected = %w[ab cd].inject({}) do |ngrams, tag|
+      ngrams.update(TaggedArtwork.all_ngrams(tag, config, false))
+    end
+    actual = Hash[coll.find.map { |document| [document['ngram'], document['score']] }]
+    expect(actual).to eq(expected)
+  end
+
+  it 'handles nil, empty, and repeated elements without duplicate records' do
+    artwork = TaggedArtwork.create!(tags: [nil, '', 'ghost', 'ghost'])
+    expect(TaggedArtwork.fulltext_search('ghost')).to eq([artwork])
+    coll = artwork.collection.database[TaggedArtwork.mongoid_fulltext_config.keys.first]
+    ngrams = coll.find.map { |document| document['ngram'] }
+    expect(ngrams).to eq(ngrams.uniq)
+  end
+
+  it 'removes old tags when the array changes or becomes empty' do
+    artwork = TaggedArtwork.create!(tags: ['ghost'])
+    artwork.update_attributes!(tags: ['accounting'])
+    expect(TaggedArtwork.fulltext_search('ghost')).to eq([])
+    expect(TaggedArtwork.fulltext_search('accounting')).to eq([artwork])
+    artwork.update_attributes!(tags: [])
+    expect(TaggedArtwork.fulltext_search('accounting')).to eq([])
+  end
+
+  it 'still indexes scalar fields when the array is nil' do
+    artwork = TaggedArtwork.create!(title: 'Painting', tags: nil)
+    expect(TaggedArtwork.fulltext_search('painting')).to eq([artwork])
+  end
+end