[Search 2.0] Match both word boundaries when filtering tags (#13554)

app/queries/homepage/articles_query.rb

@@ -69,10 +69,11 @@ module Homepage
       # would put all the previous filters in `OR` mode with tags, but what we need
       # is to only consider tags as a `OR` sub-condition
       if tags.present?
-        # `~` is the regexp operator and the `\M` modifier signifies the "end of word"
+        # `~` is the regexp operator, the `\m` modifier signifies the "beginning of word",
+        # and the `\M` modifier signifies the "end of word".
         # see https://www.postgresql.org/docs/11/functions-matching.html#FUNCTIONS-POSIX-REGEXP
         # for additional info
-        conditions = tags.map { |tag| relation.sanitize_sql_array(["cached_tag_list ~ ?", "#{tag}\\M"]) }
+        conditions = tags.map { |tag| relation.sanitize_sql_array(["cached_tag_list ~ ?", "\\m#{tag}\\M"]) }
         @relation = @relation.where(conditions.join(" OR "))
       end
 

app/services/search/postgres/reading_list.rb

@@ -94,7 +94,7 @@ module Search
         # The preferred solution, as we don't need the `Tag` model itself, is to use
         # `articles.cached_tag_list` and the `~` regexp operator with it
         tags.each do |tag|
-          relation = relation.where("articles.cached_tag_list ~ ?", "#{tag}\\M")
+          relation = relation.where("articles.cached_tag_list ~ ?", "\\m#{tag}\\M")
         end
 
         # here we issue a COUNT(*) after all the conditions are applied,

spec/queries/homepage/articles_query_spec.rb

@@ -127,11 +127,13 @@ RSpec.describe Homepage::ArticlesQuery, type: :query do
         expect(described_class.call(tags: %i[beginners ruby]).ids).to match_array([article1.id, article2.id])
       end
 
-      it "does not return results for partial matches" do
+      it "does not return results for partial matches", :aggregate_failures do
         article1.tag_list.add(:javascript)
         article1.save
 
         expect(described_class.call(tags: %i[java]).ids).to be_empty
+        expect(described_class.call(tags: %i[asc]).ids).to be_empty
+        expect(described_class.call(tags: %i[script]).ids).to be_empty
       end
     end
 

spec/services/search/postgres/reading_list_spec.rb

@@ -167,7 +167,7 @@ RSpec.describe Search::Postgres::ReadingList, type: :service do
         expect(extract_from_results(result, :path)).not_to include(article_2.path)
       end
 
-      it "does not match on partial tags" do
+      it "does not match on partial tags", :aggregate_failures do
         article_1.tag_list.add(:javascript)
         article_1.save!
 
@@ -175,6 +175,12 @@ RSpec.describe Search::Postgres::ReadingList, type: :service do
 
         result = described_class.search_documents(user, tags: [:java])
         expect(extract_from_results(result, :path)).to be_empty
+
+        result = described_class.search_documents(user, tags: [:asc])
+        expect(extract_from_results(result, :path)).to be_empty
+
+        result = described_class.search_documents(user, tags: [:script])
+        expect(extract_from_results(result, :path)).to be_empty
       end
     end