Created
June 29, 2017 16:21
-
-
Save iliabylich/836975bb029f95f3042bba36cc2b56c0 to your computer and use it in GitHub Desktop.
parslet_json_parser
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| require 'parslet' | |
| require 'json' | |
| class JSONParser < Parslet::Parser | |
| rule(:object) { str('{') >> spaces? >> object_content.maybe.as(:object) >> spaces? >> str('}') } | |
| rule(:object_content) { (kv_pair >> (comma >> kv_pair).repeat).maybe } | |
| rule(:kv_pair) { (key.as(:key) >> spaces? >> str(':') >> spaces? >> value.as(:value)).as(:kv_pair) } | |
| rule(:key) { string } | |
| rule(:value) { string | float | integer | object | array | _true | _false | null } | |
| rule(:string) { str('"') >> (str('"').absent? >> any).repeat.as(:string) >> str('"') } | |
| rule(:integer) { digits.as(:integer) } | |
| rule(:float) { (digits >> str('.') >> digits).as(:float) } | |
| rule(:array) { str('[') >> spaces? >> array_content.as(:array) >> spaces? >> str(']') } | |
| rule(:array_content) { (array_item >> (comma >> array_item).repeat).maybe } | |
| rule(:array_item) { value } | |
| rule(:_true) { str('true').as(:true) } | |
| rule(:_false) { str('false').as(:false) } | |
| rule(:null) { str('null').as(:null) } | |
| rule(:space) { match('\s') } | |
| rule(:spaces) { space >> spaces.maybe } | |
| rule(:spaces?) { spaces.maybe } | |
| rule(:comma) { spaces? >> str(',') >> spaces? } | |
| rule(:digit) { match('\d') } | |
| rule(:digits) { digit >> digits.maybe } | |
| rule(:top) { spaces? >> value >> spaces? } | |
| root(:top) | |
| end | |
| class JSONTransformer < Parslet::Transform | |
| rule(true: simple(:true)) { true } | |
| rule(false: simple(:false)) { false } | |
| rule(null: simple(:null)) { nil } | |
| rule(string: simple(:string)) { string.to_s } | |
| rule(kv_pair: { key: subtree(:key), value: subtree(:value) }) { { key => value } } | |
| rule(integer: simple(:integer)) { integer.to_i } | |
| rule(float: simple(:float)) { float.to_f } | |
| rule(array: subtree(:array)) { array } | |
| rule(object: subtree(:object)) { (object.is_a?(Array) ? object : [object]).inject(&:merge) } | |
| end | |
| json = <<-JSON | |
| { | |
| "true": true, | |
| " false": false, | |
| "null": | |
| null, | |
| "integer": | |
| 123, | |
| "float": 123.456, | |
| "string": "a string", | |
| "array": [1, 2, 3], | |
| "object": { | |
| "a": "b" | |
| } | |
| } | |
| JSON | |
| p JSON.parse(json) | |
| parser = JSONParser.new | |
| tree = parser.parse(json) | |
| transformer = JSONTransformer.new | |
| output = transformer.apply(tree) | |
| p output | |
| p JSON.parse(json) == output |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment