description_cache_store: handle empty database.

Don't perform an incremental update from a report or list of formulae if
the cache is currently empty.

Also, remove some accidentally remaining debugging output.

Library/Homebrew/description_cache_store.rb

@@ -31,6 +31,7 @@ class DescriptionCacheStore < CacheStore
   # @return [nil]
   def populate_if_empty!
     return unless database.empty?
+
     Formula.each { |f| update!(f.full_name, f.desc) }
   end
 
@@ -39,6 +40,7 @@ class DescriptionCacheStore < CacheStore
   # @param  [Report] report: an update report generated by cmd/update.rb
   # @return [nil]
   def update_from_report!(report)
+    return populate_if_empty! if database.empty?
     return if report.empty?
 
     renamings   = report.select_formula(:R)
@@ -56,11 +58,12 @@ class DescriptionCacheStore < CacheStore
   # @param  [Array] formula_names: the formulae to update.
   # @return [nil]
   def update_from_formula_names!(formula_names)
+    return populate_if_empty! if database.empty?
+
     formula_names.each do |name|
       begin
         update!(name, Formula[name].desc)
-      rescue FormulaUnavailableError, *FormulaVersions::IGNORED_EXCEPTIONS => e
+      rescue FormulaUnavailableError, *FormulaVersions::IGNORED_EXCEPTIONS
-        p e
         delete!(name)
       end
     end
@@ -71,6 +74,8 @@ class DescriptionCacheStore < CacheStore
   # @param  [Array] formula_names: the formulae to delete.
   # @return [nil]
   def delete_from_formula_names!(formula_names)
+    return if database.empty?
+
     formula_names.each(&method(:delete!))
   end
 

Library/Homebrew/test/description_cache_store_spec.rb

@@ -25,6 +25,7 @@ describe DescriptionCacheStore do
     let(:report) { double(select_formula: [], empty?: false) }
 
     it "reads from the report" do
+      expect(database).to receive(:empty?).at_least(:once).and_return(false)
       cache_store.update_from_report!(report)
     end
   end
@@ -36,6 +37,7 @@ describe DescriptionCacheStore do
         desc "desc"
       end
       expect(Formulary).to receive(:factory).with(f.name).and_return(f)
+      expect(database).to receive(:empty?).and_return(false)
       expect(database).to receive(:set).with(f.name, f.desc)
       cache_store.update_from_formula_names!([f.name])
     end
@@ -43,6 +45,7 @@ describe DescriptionCacheStore do
 
   describe "#delete_from_formula_names!" do
     it "deletes the formulae descriptions" do
+      expect(database).to receive(:empty?).and_return(false)
       expect(database).to receive(:delete).with(formula_name)
       cache_store.delete_from_formula_names!([formula_name])
     end