feat: add support for parsing general-format numbers as decimals

README.md

@@ -107,6 +107,27 @@ By default, Creek will map cell names with letter and number(A1, B3 and etc). To
 creek = Creek::Book.new file.path, with_headers: true
 ```
 
+## Handling decimals with General format
+
+When an Excel cell uses the *General* number format, Creek returns the raw
+string from the file. Numeric values such as `0.001` may therefore appear as
+`"1E-3"`. To work with the numeric value, cast it manually or enable automatic
+parsing with the `parse_general_as_number` option:
+
+```ruby
+require 'bigdecimal'
+
+creek = Creek::Book.new 'spec/fixtures/sample.xlsx', parse_general_as_number: true
+sheet = creek.sheets[0]
+
+sheet.rows.each do |row|
+  value = row['M2']
+  decimal = BigDecimal(value)
+  puts decimal.to_f # => 0.001
+end
+```
+
+Without this option, you may cast `value` manually using `BigDecimal` or `Float`.
 
 ## Contributing
 

lib/creek/book.rb

@@ -9,7 +9,8 @@ module Creek
   class Creek::Book
     attr_reader :files,
                 :shared_strings,
-                :with_headers
+                :with_headers,
+                :parse_general_as_number
 
     DATE_1900 = Date.new(1899, 12, 30).freeze
     DATE_1904 = Date.new(1904, 1, 1).freeze
@@ -24,6 +25,7 @@ def initialize(path, options = {})
       @files = Zip::File.open(path)
       @shared_strings = SharedStrings.new(self)
       @with_headers = options.fetch(:with_headers, false)
+      @parse_general_as_number = options.fetch(:parse_general_as_number, false)
     end
 
     def sheets
@@ -51,6 +53,7 @@ def sheets
             sheetfile
           )
           sheet.with_headers = with_headers
+          sheet.parse_general_as_number = parse_general_as_number
           sheet
         end
       end

lib/creek/sheet.rb

@@ -10,7 +10,8 @@ class Creek::Sheet
     HEADERS_ROW_NUMBER = '1'
     SPREADSHEETML_URI = 'http://schemas.openxmlformats.org/spreadsheetml/2006/main'
 
-    attr_accessor :with_headers
+    attr_accessor :with_headers, 
+                  :parse_general_as_number
     attr_reader :book,
                 :name,
                 :sheetid,
@@ -161,7 +162,8 @@ def convert(value, type, style_idx)
     def converter_options
       @converter_options ||= {
         shared_strings: @book.shared_strings.dictionary,
-        base_date: @book.base_date
+        base_date: @book.base_date,
+        parse_general_as_number: @book.parse_general_as_number
       }
     end
 

lib/creek/styles/converter.rb

@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require 'set'
+require 'bigdecimal'
 
 module Creek
   class Styles
@@ -30,6 +31,7 @@ class Converter
       # - base_date: from what date to begin, see method #base_date
 
       DATE_TYPES = %i[date time date_time].to_set
+      NUMERIC_REGEXP = /\A-?(?:\d+(?:\.\d+)?|\d*\.\d+)(?:[eE][+-]?\d+)?\z/.freeze
       def self.call(value, type, style, options = {})
         return nil if value.nil? || value.empty?
 
@@ -59,9 +61,13 @@ def self.call(value, type, style, options = {})
         ##
 
         when :string
-          value
+          if options[:parse_general_as_number] && numeric_string?(value)
+            convert_general_number(value)
+          else
+            value
+          end
         when :unsupported
-          convert_unknown(value)
+          convert_unknown(value, options)
         when :fixnum
           value.to_i
         when :float, :percentage
@@ -75,13 +81,15 @@ def self.call(value, type, style, options = {})
 
         ## Nothing matched
         else
-          convert_unknown(value)
+          convert_unknown(value, options)
         end
       end
 
-      def self.convert_unknown(value)
-        if value.nil? or value.empty?
+      def self.convert_unknown(value, options = {})
+        if value.nil? || value.empty?
           value
+        elsif options[:parse_general_as_number] && numeric_string?(value)
+          convert_general_number(value)
         elsif value.to_i.to_s == value.to_s
           value.to_i
         elsif value.to_f.to_s == value.to_s
@@ -129,6 +137,18 @@ def self.round_datetime(datetime_string)
 
         ::Time.new(yyyy.to_i, mm.to_i, dd.to_i, hh.to_i, mi.to_i, ss.to_r).round(0)
       end
+
+      def self.numeric_string?(value)
+        value.match?(NUMERIC_REGEXP)
+      end
+
+      def self.convert_general_number(value)
+        if defined?(BigDecimal)
+          BigDecimal(value)
+        else
+          value.to_f
+        end
+      end
     end
   end
 end

spec/test_spec.rb

@@ -76,6 +76,25 @@
   end
 end
 
+describe 'Creek parsing a file with large numbers with automatic conversion' do
+  before(:all) do
+    @creek = Creek::Book.new 'spec/fixtures/large_numbers.xlsx', parse_general_as_number: true
+    @expected_simple_rows = [{ 'A' => 783_294_732.0, 'B' => '783294732', 'C' => 783_294_732.0 }]
+  end
+
+  after(:all) do
+    @creek.close
+  end
+
+  it 'casts general numbers to floats' do
+    rows = []
+    @creek.sheets[0].simple_rows.each do |row|
+      rows << row
+    end
+    expect(rows[0]).to eq(@expected_simple_rows[0])
+  end
+end
+
 describe 'Creek parsing a sample XLSX file' do
   before(:all) do
     @creek = Creek::Book.new 'spec/fixtures/sample.xlsx'