Expand spec coverage and refactor the `Account.find_` methods (#3485)

* Move specs for account finder methods to concern spec

* Move account finder methods to concern

* Improve spec wording

* Use more explicit comparison to ensure correct return value

* Add coverage for .find_local! and .find_remote!

* Add some methods to the finder

* Use arel on matching_username method

* Avoid ternary in matching domain method

* Simplify finder methods

* Use an AccountFinder class to simplify lookup

4 files changed, 152 insertions, 69 deletions

diff --git a/app/models/account.rb b/app/models/account.rb
index cb116dbaf..4561fd0a4 100644
--- a/app/models/account.rb
+++ b/app/models/account.rb
@@ -42,6 +42,7 @@ class Account < ApplicationRecord
   MENTION_RE = /(?:^|[^\/[:word:]])@([a-z0-9_]+(?:@[a-z0-9\.\-]+[a-z0-9]+)?)/i
 
   include AccountAvatar
+  include AccountFinderConcern
   include AccountHeader
   include AccountInteractions
   include Attachmentable
@@ -162,27 +163,6 @@ class Account < ApplicationRecord
   end
 
   class << self
-    def find_local!(username)
-      find_remote!(username, nil)
-    end
-
-    def find_remote!(username, domain)
-      raise ActiveRecord::RecordNotFound if username.blank?
-      where('lower(accounts.username) = ?', username.downcase).where(domain.nil? ? { domain: nil } : 'lower(accounts.domain) = ?', domain&.downcase).take!
-    end
-
-    def find_local(username)
-      find_local!(username)
-    rescue ActiveRecord::RecordNotFound
-      nil
-    end
-
-    def find_remote(username, domain)
-      find_remote!(username, domain)
-    rescue ActiveRecord::RecordNotFound
-      nil
-    end
-
     def triadic_closures(account, limit: 5, offset: 0)
       sql = <<-SQL.squish
         WITH first_degree AS (
diff --git a/app/models/concerns/account_finder_concern.rb b/app/models/concerns/account_finder_concern.rb
new file mode 100644
index 000000000..d3ad519b1
--- /dev/null
+++ b/app/models/concerns/account_finder_concern.rb
@@ -0,0 +1,58 @@
+# frozen_string_literal: true
+
+module AccountFinderConcern
+  extend ActiveSupport::Concern
+
+  class_methods do
+    def find_local!(username)
+      find_local(username) || raise(ActiveRecord::RecordNotFound)
+    end
+
+    def find_remote!(username, domain)
+      find_remote(username, domain) || raise(ActiveRecord::RecordNotFound)
+    end
+
+    def find_local(username)
+      find_remote(username, nil)
+    end
+
+    def find_remote(username, domain)
+      AccountFinder.new(username, domain).account
+    end
+  end
+
+  class AccountFinder
+    attr_reader :username, :domain
+
+    def initialize(username, domain)
+      @username = username
+      @domain = domain
+    end
+
+    def account
+      scoped_accounts.take
+    end
+
+    private
+
+    def scoped_accounts
+      Account.unscoped.tap do |scope|
+        scope.merge! matching_username
+        scope.merge! matching_domain
+      end
+    end
+
+    def matching_username
+      raise(ActiveRecord::RecordNotFound) if username.blank?
+      Account.where(Account.arel_table[:username].lower.eq username.downcase)
+    end
+
+    def matching_domain
+      if domain.nil?
+        Account.where(domain: nil)
+      else
+        Account.where(Account.arel_table[:domain].lower.eq domain.downcase)
+      end
+    end
+  end
+end
diff --git a/spec/models/account_spec.rb b/spec/models/account_spec.rb
index 08098854b..ebec463e1 100644
--- a/spec/models/account_spec.rb
+++ b/spec/models/account_spec.rb
@@ -301,54 +301,6 @@ RSpec.describe Account, type: :model do
     end
   end
 
-  describe '.find_local' do
-    before do
-      Fabricate(:account, username: 'Alice')
-    end
-
-    it 'returns Alice for alice' do
-      expect(Account.find_local('alice')).to_not be_nil
-    end
-
-    it 'returns Alice for Alice' do
-      expect(Account.find_local('Alice')).to_not be_nil
-    end
-
-    it 'does not return anything for a_ice' do
-      expect(Account.find_local('a_ice')).to be_nil
-    end
-
-    it 'does not return anything for al%' do
-      expect(Account.find_local('al%')).to be_nil
-    end
-  end
-
-  describe '.find_remote' do
-    before do
-      Fabricate(:account, username: 'Alice', domain: 'mastodon.social')
-    end
-
-    it 'returns Alice for alice@mastodon.social' do
-      expect(Account.find_remote('alice', 'mastodon.social')).to_not be_nil
-    end
-
-    it 'returns Alice for ALICE@MASTODON.SOCIAL' do
-      expect(Account.find_remote('ALICE', 'MASTODON.SOCIAL')).to_not be_nil
-    end
-
-    it 'does not return anything for a_ice@mastodon.social' do
-      expect(Account.find_remote('a_ice', 'mastodon.social')).to be_nil
-    end
-
-    it 'does not return anything for alice@m_stodon.social' do
-      expect(Account.find_remote('alice', 'm_stodon.social')).to be_nil
-    end
-
-    it 'does not return anything for alice@m%' do
-      expect(Account.find_remote('alice', 'm%')).to be_nil
-    end
-  end
-
   describe '.following_map' do
     it 'returns an hash' do
       expect(Account.following_map([], 1)).to be_a Hash
diff --git a/spec/models/concerns/account_finder_concern_spec.rb b/spec/models/concerns/account_finder_concern_spec.rb
new file mode 100644
index 000000000..05f0f44f2
--- /dev/null
+++ b/spec/models/concerns/account_finder_concern_spec.rb
@@ -0,0 +1,93 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe AccountFinderConcern do
+  describe 'local finders' do
+    before do
+      @account = Fabricate(:account, username: 'Alice')
+    end
+
+    describe '.find_local' do
+      it 'returns case-insensitive result' do
+        expect(Account.find_local('alice')).to eq(@account)
+      end
+
+      it 'returns correctly cased result' do
+        expect(Account.find_local('Alice')).to eq(@account)
+      end
+
+      it 'returns nil without a match' do
+        expect(Account.find_local('a_ice')).to be_nil
+      end
+
+      it 'returns nil for regex style username value' do
+        expect(Account.find_local('al%')).to be_nil
+      end
+    end
+
+    describe '.find_local!' do
+      it 'returns matching result' do
+        expect(Account.find_local!('alice')).to eq(@account)
+      end
+
+      it 'raises on non-matching result' do
+        expect { Account.find_local!('missing') }.to raise_error(ActiveRecord::RecordNotFound)
+      end
+
+      it 'raises with blank username' do
+        expect { Account.find_local!('') }.to raise_error(ActiveRecord::RecordNotFound)
+      end
+
+      it 'raises with nil username' do
+        expect { Account.find_local!(nil) }.to raise_error(ActiveRecord::RecordNotFound)
+      end
+    end
+  end
+
+  describe 'remote finders' do
+    before do
+      @account = Fabricate(:account, username: 'Alice', domain: 'mastodon.social')
+    end
+
+    describe '.find_remote' do
+      it 'returns exact match result' do
+        expect(Account.find_remote('alice', 'mastodon.social')).to eq(@account)
+      end
+
+      it 'returns case-insensitive result' do
+        expect(Account.find_remote('ALICE', 'MASTODON.SOCIAL')).to eq(@account)
+      end
+
+      it 'returns nil when username does not match' do
+        expect(Account.find_remote('a_ice', 'mastodon.social')).to be_nil
+      end
+
+      it 'returns nil when domain does not match' do
+        expect(Account.find_remote('alice', 'm_stodon.social')).to be_nil
+      end
+
+      it 'returns nil for regex style domain value' do
+        expect(Account.find_remote('alice', 'm%')).to be_nil
+      end
+    end
+
+    describe '.find_remote!' do
+      it 'returns matching result' do
+        expect(Account.find_remote!('alice', 'mastodon.social')).to eq(@account)
+      end
+
+      it 'raises on non-matching result' do
+        expect { Account.find_remote!('missing', 'mastodon.host') }.to raise_error(ActiveRecord::RecordNotFound)
+      end
+
+      it 'raises with blank username' do
+        expect { Account.find_remote!('', '') }.to raise_error(ActiveRecord::RecordNotFound)
+      end
+
+      it 'raises with nil username' do
+        expect { Account.find_remote!(nil, nil) }.to raise_error(ActiveRecord::RecordNotFound)
+      end
+    end
+  end
+end