module Sprockets::ProcessorUtils
Functional utilities for dealing with Processor functions.
A Processor is a general function that my modify or transform an asset as part of the pipeline. CoffeeScript to JavaScript conversion, Minification or Concatenation are all implemented as seperate Processor steps.
Processors maybe any object that responds to call. So procs or a class that defines a self.call method.
For ergonomics, processors may return a number of shorthand values. Unfortunately, this means that processors can not compose via ordinary function composition. The composition helpers here can help.
Constants
- VALID_METADATA_COMPOUND_TYPES
Internal: Set of all nested compound metadata types that can nest values.
- VALID_METADATA_COMPOUND_TYPES_HASH
Internal: Hash of all nested compound metadata types that can nest values.
- VALID_METADATA_TYPES
Internal: Set of all allowed metadata types.
- VALID_METADATA_VALUE_TYPES
Internal: Set of all “simple” value types allowed to be returned in processor metadata.
- VALID_METADATA_VALUE_TYPES_HASH
Internal: Hash of all “simple” value types allowed to be returned in processor metadata.
Public Instance Methods
Public: Invoke processor.
processor - Processor callables input - Hash of input data to pass to processor
Returns a Hash with :data and other processor metadata key/values.
# File lib/sprockets/processor_utils.rb, line 71 def call_processor(processor, input) metadata = (input[:metadata] || {}).dup metadata[:data] = input[:data] case result = processor.call({data: "", metadata: {}}.merge(input)) when NilClass metadata when Hash metadata.merge(result) when String metadata.merge(data: result) else raise TypeError, "invalid processor return type: #{result.class}" end end
Public: Invoke list of processors in right to left order.
The right to left order processing mirrors standard function composition. Think about:
bundle.call(uglify.call(coffee.call(input)))
processors - Array of processor callables input - Hash of input data to pass to each processor
Returns a Hash with :data and other processor metadata key/values.
# File lib/sprockets/processor_utils.rb, line 52 def call_processors(processors, input) data = input[:data] || "" metadata = (input[:metadata] || {}).dup processors.reverse_each do |processor| result = call_processor(processor, input.merge(data: data, metadata: metadata)) data = result.delete(:data) metadata.merge!(result) end metadata.merge(data: data) end
Public: Compose processors in right to left order.
processors - Array of processors callables
Returns a composed Proc.
# File lib/sprockets/processor_utils.rb, line 24 def compose_processors(*processors) context = self if processors.length == 1 obj = method(:call_processor).to_proc.curry[processors.first] else obj = method(:call_processors).to_proc.curry[processors] end metaclass = (class << obj; self; end) metaclass.send(:define_method, :cache_key) do context.processors_cache_keys(processors) end obj end
Internal: Get processor defined cached key.
processor - Processor function
Returns JSON serializable key or nil.
# File lib/sprockets/processor_utils.rb, line 92 def processor_cache_key(processor) processor.cache_key if processor.respond_to?(:cache_key) end
Internal: Get combined cache keys for set of processors.
processors - Array of processor functions
Returns Array of JSON serializable keys.
# File lib/sprockets/processor_utils.rb, line 101 def processors_cache_keys(processors) processors.map { |processor| processor_cache_key(processor) } end
Internal: Validate object is in validate metadata whitelist.
value - Any Object
Returns true if class is in whitelist otherwise false.
# File lib/sprockets/processor_utils.rb, line 170 def valid_processor_metadata_value?(value) if VALID_METADATA_VALUE_TYPES_HASH[value.class] true elsif VALID_METADATA_COMPOUND_TYPES_HASH[value.class] value.all? { |v| valid_processor_metadata_value?(v) } else false end end
Internal: Validate returned result of calling a processor pipeline and raise a friendly user error message.
result - Metadata Hash returned from call_processors
Returns result or raises a TypeError.
# File lib/sprockets/processor_utils.rb, line 142 def validate_processor_result!(result) if !result.instance_of?(Hash) raise TypeError, "processor metadata result was expected to be a Hash, but was #{result.class}" end if !result[:data].instance_of?(String) raise TypeError, "processor :data was expected to be a String, but as #{result[:data].class}" end result.each do |key, value| if !key.instance_of?(Symbol) raise TypeError, "processor metadata[#{key.inspect}] expected to be a Symbol" end if !valid_processor_metadata_value?(value) raise TypeError, "processor metadata[:#{key}] returned a complex type: #{value.inspect}\n" + "Only #{VALID_METADATA_TYPES.to_a.join(", ")} maybe used." end end result end