Expose which search strategy produced each result

query_packages now assigns @search_sources - a hash mapping package
ids to the matching strategy that put them into the results: :exact,
:name_prefix, :name_contains, :semantic or :fulltext. The grid and
list views render a small badge with a humanized label per result,
making the search tiers observable. semantic_results() was folded
into search_packages() so each branch tags its own source. Adds the
rails-controller-testing gem for assigns() in tests.

app/controllers/packages_controller.rb

@@ -362,6 +362,11 @@ class PackagesController < ApplicationController
   def query_packages
     packages = Package # .order(visits: :desc)
 
+    # Maps package id to the search strategy that put it into the
+    # result list: :exact, :name_prefix, :name_contains, :semantic or
+    # :fulltext. Empty when browsing without a search term.
+    @search_sources = {}
+
     # text search
     if params[:search].present?
       logger.debug "Searching for #{params[:search]}"
@@ -393,15 +398,34 @@ class PackagesController < ApplicationController
 
   def search_packages(query)
     exact_match = Package.find_by(name: query)
-    return Package.where(id: exact_match.id) if exact_match
+    if exact_match
+      @search_sources[exact_match.id] = :exact
+      return Package.where(id: exact_match.id)
+    end
 
-    tokens = query.to_s.split(/\s+/)
-    name_matches = (
-      Package.name_starts_with(query).limit(MAX_PROMOTED_NAME_MATCHES) +
-      Package.name_contains_all(tokens).limit(MAX_PROMOTED_NAME_MATCHES)
-    ).uniq(&:id)
+    prefix_matches = Package.name_starts_with(query).limit(MAX_PROMOTED_NAME_MATCHES).to_a
+    token_matches = Package.name_contains_all(query.to_s.split(/\s+/)).limit(
+      MAX_PROMOTED_NAME_MATCHES
+    ).to_a
+    prefix_matches.each { |package| @search_sources[package.id] ||= :name_prefix }
+    token_matches.each { |package| @search_sources[package.id] ||= :name_contains }
 
-    results = (name_matches + semantic_results(query)).uniq(&:id)
+    semantic = []
+    if Package.lexical_overlap?(query)
+      begin
+        semantic = Package.nearest_to_text(query, limit: MAX_SEMANTIC_RESULTS).to_a
+        semantic.each { |package| @search_sources[package.id] ||= :semantic }
+      rescue Vectorizer::Error => e
+        logger.error "Semantic search failed: #{e.message}"
+        flash.now['error'] = 'Semantic search is unavailable right now. Showing full-text matches.'
+        semantic = Package.general_search(query).limit(100).to_a
+        semantic.each { |package| @search_sources[package.id] ||= :fulltext }
+      end
+    else
+      logger.debug "Query '#{query}' has no lexical overlap with package data"
+    end
+
+    results = (prefix_matches + token_matches + semantic).uniq(&:id)
 
     # Queries that share no vocabulary with our package data can produce
     # no meaningful results. Skip the vector service round-trip and show
@@ -409,23 +433,6 @@ class PackagesController < ApplicationController
     results.empty? ? Package.none : results
   end
 
-  # Semantic (vector) nearest neighbor search with a full-text fallback
-  # for when the external embedding service is unreachable.
-  def semantic_results(query)
-    unless Package.lexical_overlap?(query)
-      logger.debug "Query '#{query}' has no lexical overlap with package data"
-      return []
-    end
-
-    begin
-      Package.nearest_to_text(query, limit: MAX_SEMANTIC_RESULTS).to_a
-    rescue Vectorizer::Error => e
-      logger.error "Semantic search failed: #{e.message}"
-      flash.now['error'] = 'Semantic search is unavailable right now. Showing full-text matches.'
-      Package.general_search(query).limit(100).to_a
-    end
-  end
-
   # Store a random identifier and the client's IP address in the session
   # for later identification.
   # def create_user_token

app/helpers/packages_helper.rb

@@ -1,4 +1,16 @@
 module PackagesHelper
+  # Human readable label for the search strategy that put a package
+  # into the search results (see PackagesController#search_packages)
+  def search_source_label(source)
+    {
+      exact: 'exact match',
+      name_prefix: 'name match',
+      name_contains: 'name match',
+      semantic: 'similar',
+      fulltext: 'full-text'
+    }[source]
+  end
+
   # Return the description and/or the version of the package
   def screenshot_caption(screenshot)
     str = []

app/views/packages/browse.slim

@@ -24,6 +24,9 @@
                   = pkg.name
                 .text
                   = pkg.description
+                - if @search_sources[pkg.id]
+                  .text.search-source
+                    span.label.secondary = search_source_label(@search_sources[pkg.id])
       - elsif @view_style==:list
         - @packages.to_a.each do |pkg|
           .grid-x.grid-margin-x.listview
@@ -37,6 +40,9 @@
                 a href=package_path(name: pkg.name)
                   =pkg.name
               p =pkg.description
+              - if @search_sources[pkg.id]
+                p
+                  span.label.secondary = search_source_label(@search_sources[pkg.id])
               .listview.longdescription
                 = pkg.long_description_first_paragraph