Module: Sprockets::ProcessorUtils

Extended by:
ProcessorUtils
Included in:
Sprockets, Loader, Processing, ProcessorUtils, Transformers
Defined in:
lib/sprockets/processor_utils.rb

Overview

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.

Constant Summary collapse

VALID_METADATA_VALUE_TYPES =

Internal: Set of all “simple” value types allowed to be returned in processor metadata.

Set.new([
  String,
  Symbol,
  Fixnum,
  Bignum,
  TrueClass,
  FalseClass,
  NilClass
]).freeze
VALID_METADATA_COMPOUND_TYPES =

Internal: Set of all nested compound metadata types that can nest values.

Set.new([
  Array,
  Hash,
  Set
]).freeze
VALID_METADATA_TYPES =

Internal: Set of all allowed metadata types.

(VALID_METADATA_VALUE_TYPES + VALID_METADATA_COMPOUND_TYPES).freeze

Instance Method Summary collapse

Instance Method Details

#call_processor(processor, input) ⇒ Object

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.



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# 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

#call_processors(processors, input) ⇒ Object

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.



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# 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

#compose_processors(*processors) ⇒ Object

Public: Compose processors in right to left order.

processors - Array of processors callables

Returns a composed Proc.



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# 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

#processor_cache_key(processor) ⇒ Object

Internal: Get processor defined cached key.

processor - Processor function

Returns JSON serializable key or nil.



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# File 'lib/sprockets/processor_utils.rb', line 92

def processor_cache_key(processor)
  processor.cache_key if processor.respond_to?(:cache_key)
end

#processors_cache_keys(processors) ⇒ Object

Internal: Get combined cache keys for set of processors.

processors - Array of processor functions

Returns Array of JSON serializable keys.



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# File 'lib/sprockets/processor_utils.rb', line 101

def processors_cache_keys(processors)
  processors.map { |processor| processor_cache_key(processor) }
end

#valid_processor_metadata_value?(value) ⇒ Boolean

Internal: Validate object is in validate metadata whitelist.

value - Any Object

Returns true if class is in whitelist otherwise false.

Returns:

  • (Boolean) 


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# File 'lib/sprockets/processor_utils.rb', line 161

def valid_processor_metadata_value?(value)
  if VALID_METADATA_VALUE_TYPES.include?(value.class)
    true
  elsif VALID_METADATA_COMPOUND_TYPES.include?(value.class)
    value.all? { |v| valid_processor_metadata_value?(v) }
  else
    false
  end
end

#validate_processor_result!(result) ⇒ Object

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.



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# File 'lib/sprockets/processor_utils.rb', line 133

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