Rake task to export default settings as seeds

README.md

@@ -118,6 +118,15 @@ Tests need to be run from within toplevel application directory:
 
         bundle exec rails test test/system/users_test.rb --seed 1234
 
+
 ### Icons
 
 Pictogrammers Material Design Icons: https://pictogrammers.com/library/mdi/
+
+
+### Rake tasks
+
+Exporting default settings defined in application to seed file (e.g. to send as
+PR or share between installations):
+
+        bundle exec rails db:seed:export

config/initializers/core_ext.rb

@@ -0,0 +1 @@
+require 'core_ext/big_decimal/formatting'

db/seeds.rb

@@ -20,19 +20,4 @@ end
 # Formulas will be deleted as dependent on Quantities
 #[Source, Quantity, Unit].each { |model| model.defaults.delete_all }
 
-Unit.transaction do
-  Unit.defaults.delete_all
-
-  unit_1 = Unit.create symbol: "1",   name: "dimensionless, one"
-           Unit.create symbol: "%",   base: unit_1, multiplier: 1e-2, name: "percent"
-           Unit.create symbol: "‰",   base: unit_1, multiplier: 1e-3, name: "promille"
-           Unit.create symbol: "‱",   base: unit_1, multiplier: 1e-4, name: "basis point"
-           Unit.create symbol: "ppm", base: unit_1, multiplier: 1e-6, name: "parts per million"
-
-  unit_g = Unit.create symbol: "g",  name: "gram"
-           Unit.create symbol: "ug", base: unit_g, multiplier: 1e-6, name: "microgram"
-           Unit.create symbol: "mg", base: unit_g, multiplier: 1e-3, name: "milligram"
-           Unit.create symbol: "kg", base: unit_g, multiplier: 1e3,  name: "kilogram"
-
-  Unit.create symbol: "kcal", name: "kilocalorie"
-end
+require 'seeds/units.rb'

db/seeds/templates/units.erb

@@ -0,0 +1,9 @@
+Unit.transaction do
+  Unit.defaults.delete_all
+<% Unit.defaults.ordered.each do |unit| %>
+<%= "\n" if unit.base.nil? %>
+  unit_<%= unit.symbol %> =
+    Unit.create symbol: "<%= unit.symbol %>",<% unless unit.base.nil? %> base: unit_<%= unit.base.symbol %>, multiplier: <%= unit.multiplier.to_scientific %>,<% end %>
+                description: "<%= unit.description %>"
+<% end %>
+end

db/seeds/units.rb

@@ -0,0 +1,36 @@
+Unit.transaction do
+  Unit.defaults.delete_all
+
+  unit_1 =
+    Unit.create symbol: "1",
+                description: "dimensionless, one"
+  unit_ppm =
+    Unit.create symbol: "ppm", base: unit_1, multiplier: 1e-6,
+                description: "parts per million"
+  unit_‱ =
+    Unit.create symbol: "‱", base: unit_1, multiplier: 1e-4,
+                description: "basis point"
+  unit_‰ =
+    Unit.create symbol: "‰", base: unit_1, multiplier: 1e-3,
+                description: "promille"
+  unit_% =
+    Unit.create symbol: "%", base: unit_1, multiplier: 1e-2,
+                description: "percent"
+
+  unit_g =
+    Unit.create symbol: "g",
+                description: "gram"
+  unit_ug =
+    Unit.create symbol: "ug", base: unit_g, multiplier: 1e-6,
+                description: "microgram"
+  unit_mg =
+    Unit.create symbol: "mg", base: unit_g, multiplier: 1e-3,
+                description: "milligram"
+  unit_kg =
+    Unit.create symbol: "kg", base: unit_g, multiplier: 1e3,
+                description: "kilogram"
+
+  unit_kcal =
+    Unit.create symbol: "kcal",
+                description: "kilocalorie"
+end

lib/core_ext/big_decimal/formatting.rb

@@ -0,0 +1,14 @@
+module FixinMe
+  module BigDecimalScientificNotation
+    def to_scientific
+      return 'NaN' unless finite?
+
+      sign, coefficient, base, exponent = split
+      (sign == -1 ? '-' : '') +
+        (coefficient.length > 1 ? coefficient.insert(1, '.') : coefficient) +
+        (exponent != 1 ? "e#{exponent-1}" : '')
+    end
+  end
+end
+
+BigDecimal.prepend(FixinMe::BigDecimalScientificNotation)

lib/tasks/db.rake

@@ -0,0 +1,12 @@
+namespace :db do
+  namespace :seed do
+    desc "Dump default settings as seed data to db/seeds/*.rb"
+    task export: :environment do
+      seeds_path = Pathname.new(Rails.application.paths["db"].first) / 'seeds'
+      (seeds_path / 'templates').glob('*.erb').each do |template_path|
+        template = ERB.new(template_path.read, trim_mode: '<>')
+        (seeds_path / "#{template_path.basename('.*').to_s}.rb").write(template.result)
+      end
+    end
+  end
+end