parser-transform/test/json.coffee.md

Streaming+Async lexer and parser

A starter JSON lexer

    {expect} = require 'chai'

    fs = require 'fs'
    json_lexer  = fs.readFileSync 'test/json.l','utf8'
    json_parser = fs.readFileSync 'test/json.y', 'utf8'
    asyncjson_parser = fs.readFileSync 'test/json-async.y', 'utf8'

    Stream = require 'stream'

    class Tee extends Stream.Transform
      constructor: (options = {}) ->
        options.objectMode = true
        super options
      _transform: (chunk,encoding,next) ->
        console.log chunk
        @push chunk
        next()
        return

    class LongReadable extends Stream.Readable
      constructor: (options) ->
        super options
        @count = 0

      _read: (size) ->
        switch @count++
          when 0
            @push '['
          when 21
            @push '4'
          when 22
            @push ']'
          when 23
            setTimeout (=> @push null), 60
          else
            setTimeout (=> @push '"yes",'), 50
        return

    describe 'The module', ->
      {LexerParser,LexerTransform,Grammar,ParserTransform} = require '..'

      dfas = null
      grammar = null
      grammar2 = null

      it 'should build a lexer', ->
        dfas = LexerParser.parse json_lexer

      it 'should build a grammar', ->

        grammar = Grammar.fromString json_parser, mode:'LALR1', 'bnf'

      it 'should build another grammar', ->

        grammar2 = Grammar.fromString asyncjson_parser, mode:'LALR1', 'bnf'

      it 'should parse two concurrent streams', (done) ->

Test three concurrent streams

A stream is read from `package.json`

        s = fs.createReadStream('./package.json','utf8')
        s.setEncoding('utf8')
        streamLexer = new LexerTransform dfas
        streamParser = new ParserTransform grammar

The "background" stream is generated by code.

        w = new LongReadable
        w.setEncoding 'utf8'
        streamLexer2 = new LexerTransform dfas
        streamParser2 = new ParserTransform grammar

A third stream is read from `rows.json`

        r = fs.createReadStream('./test/rows.json','utf8')
        r.setEncoding('utf8')
        streamLexer3 = new LexerTransform dfas
        streamParser3 = new ParserTransform grammar2

All three streams are expected to complete.

        counted = 3

        s
          .pipe streamLexer
          .pipe streamParser
          .on 'data', (data) ->
            expect(data).to.have.property 'name', 'parser-transform'
            expect(data).to.have.property('scripts').with.property('test')
            done() if --counted is 0

        w
          .pipe streamLexer2
          # .pipe new Tee # use this to see chunks generated by the lexer
          .pipe streamParser2
          # .pipe new Tee # use this to see chunks generated by the parser
          .on 'data', (data) ->
            expect(data).to.have.length 21
            expect(data).to.have.property 0, 'yes'
            expect(data).to.have.property 1, 'yes'
            expect(data).to.have.property 20, 4
            done() if --counted is 0

        expected_rows = 3
        r
          .pipe streamLexer3
          .pipe streamParser3
          .on 'data', (data) ->
            expect(data).to.have.property('prefix').with.length(2)
            expect(data).to.have.property('prefix').with.property(0,'rows')
            expect(data).to.have.property('value').with.property('_id')
            return unless --expected_rows is 0
            done() if --counted is 0

        return