DEV: Add `isValidUrl` helper function to theme migrations (#26817)

This commit adds a `isValidUrl` helper function to the context in
which theme migrations are ran in. This helper function is to make it
easier for theme developers to check if a string is a valid URL or path
when writing theme migrations. This can be helpful in cases when
migrating a string based setting to `type: objects` which contain `type:
string` properties with URL validations enabled.

This commit also introduces the `UrlHelper.is_valid_url?` method
which actually checks that the URL string is of the valid format instead of
only checking if the URL string is parseable which is what `UrlHelper.relaxed_parse` does
and is not sufficient for our needs.

app/services/theme_settings_migrations_runner.rb

@@ -15,6 +15,12 @@ class ThemeSettingsMigrationsRunner
     def get_category_id_by_name(category_name)
       Category.where(name_lower: category_name).pick(:id)
     end
+
+    # @param [String] URL string to check if it is a valid absolute URL, path or anchor.
+    # @return [Boolean] True if the URL is a valid URL or path, false otherwise.
+    def is_valid_url(url)
+      UrlHelper.is_valid_url?(url)
+    end
   end
 
   Migration = Struct.new(:version, :name, :original_name, :code, :theme_field_id)

lib/theme_settings_object_validator.rb

@@ -188,7 +188,7 @@ class ThemeSettingsObjectValidator
         return false
       end
 
-      if validations&.dig(:url) && !UrlHelper.relaxed_parse(value)
+      if validations&.dig(:url) && !UrlHelper.is_valid_url?(value)
         add_error(property_name, :string_value_not_valid_url)
         return false
       end

lib/url_helper.rb

@@ -24,6 +24,29 @@ class UrlHelper
   rescue URI::Error
   end
 
+  # Heuristic checks to determine if the URL string is a valid absolute URL, path or anchor
+  def self.is_valid_url?(url)
+    uri = URI.parse(url)
+
+    return true if uri.is_a?(URI::Generic) && url.starts_with?("/") || url.match?(/\A\#([^#]*)/)
+
+    if uri.scheme
+      return true if uri.is_a?(URI::MailTo)
+
+      if url.match?(%r{\A#{uri.scheme}://[^/]}) &&
+           (
+             uri.is_a?(URI::HTTP) || uri.is_a?(URI::HTTPS) || uri.is_a?(URI::FTP) ||
+               uri.is_a?(URI::LDAP)
+           )
+        return true
+      end
+    end
+
+    false
+  rescue URI::InvalidURIError
+    false
+  end
+
   def self.encode_and_parse(url)
     URI.parse(Addressable::URI.encode(url))
   end

spec/lib/theme_settings_object_validator_spec.rb

@@ -424,7 +424,7 @@ RSpec.describe ThemeSettingsObjectValidator do
         expect(errors["/string_property"].full_messages).to contain_exactly("must be a string")
       end
 
-      it "should not return an empty hash when string property satsify url validation" do
+      it "should not return an empty hash when string property satisfy url validation" do
         schema = {
           name: "section",
           properties: {

spec/lib/url_helper_spec.rb

@@ -271,4 +271,53 @@ RSpec.describe UrlHelper do
       expect(described_class.rails_route_from_url(url)).to eq(nil)
     end
   end
+
+  describe ".is_valid_url?" do
+    it "should return true for a valid HTTP URL" do
+      expect(described_class.is_valid_url?("http://www.example.com")).to eq(true)
+    end
+
+    it "should return true for a valid HTTPS URL" do
+      expect(described_class.is_valid_url?("https://www.example.com")).to eq(true)
+    end
+
+    it "should return true for a valid FTP URL" do
+      expect(described_class.is_valid_url?("ftp://example.com")).to eq(true)
+    end
+
+    it "should return true for a valid mailto URL" do
+      expect(described_class.is_valid_url?("mailto:someone@discourse.org")).to eq(true)
+    end
+
+    it "should return true for a valid LDAP URL" do
+      expect(described_class.is_valid_url?("ldap://ldap.example.com/dc=example;dc=com?quer")).to eq(
+        true,
+      )
+    end
+
+    it "should return true for a path" do
+      expect(described_class.is_valid_url?("/some/path")).to eq(true)
+    end
+
+    it "should return true for a path with query params" do
+      expect(described_class.is_valid_url?("/some/path?query=param")).to eq(true)
+    end
+
+    it "should return true for anchor links" do
+      expect(described_class.is_valid_url?("#anchor")).to eq(true)
+      expect(described_class.is_valid_url?("#")).to eq(true)
+    end
+
+    it "should return false for invalid urls" do
+      expect(described_class.is_valid_url?("")).to eq(false)
+      expect(described_class.is_valid_url?("http//www.example.com")).to eq(false)
+      expect(described_class.is_valid_url?("http:/www.example.com")).to eq(false)
+      expect(described_class.is_valid_url?("https:///www.example.com")).to eq(false)
+      expect(described_class.is_valid_url?("mailtoooo:someone@discourse.org")).to eq(false)
+      expect(described_class.is_valid_url?("ftp://")).to eq(false)
+      expect(described_class.is_valid_url?("http://")).to eq(false)
+      expect(described_class.is_valid_url?("https://")).to eq(false)
+      expect(described_class.is_valid_url?("ldap://")).to eq(false)
+    end
+  end
 end

spec/services/theme_settings_migrations_runner_spec.rb

@@ -336,6 +336,25 @@ describe ThemeSettingsMigrationsRunner do
       expect(results[0][:settings_after]).to eq({})
     end
 
+    it "attaches the isValidUrl() function to the context of the migrations" do
+      theme.update_setting(:string_setting, "https://google.com")
+      theme.save!
+
+      migration_field.update!(value: <<~JS)
+        export default function migrate(settings, helpers) {
+          if (!helpers.isValidUrl("some_invalid_string")) {
+            settings.set("string_setting", "is_not_valid_string");
+          }
+
+          return settings;
+        }
+      JS
+
+      results = described_class.new(theme).run
+
+      expect(results[0][:settings_after]).to eq({ "string_setting" => "is_not_valid_string" })
+    end
+
     it "attaches the getCategoryIdByName() function to the context of the migrations" do
       category = Fabricate(:category, name: "some-category")