elm-xml-decode

XML decoder, sharing the spirit of Json.Decode.

Using jinjor/elm-xml-parser as its parser component.

Related Works

eeue56/elm-xml is an existing full-package XML parser/decoder for Elm, though I intend to provide an alternative XML decoder which exhibits following properties:

• Provides Decoder-based APIs, sharing the spirit of Json.Decode
• Also provides DSL-styled decoder compositions, sharing the sprits of Json.Decode.Pipeline
• Handles list of XML node with identical tags, using ListDecoder type
• Locates targeting XML nodes using "path" of tags, partially mimicking XPath

Examples

Basics:

import Xml.Decode exposing (..)

type alias Data =
    { string : String
    , integers : List Int
    }

dataDecoder : Decoder Data
dataDecoder =
    map2 Data
        (path [ "path", "to", "string", "value" ] (single string))
        (path [ "path", "to", "int", "values" ] (list int))

run dataDecoder
    """
    <root>
        <path>
            <to>
                <string>
                    <value>SomeString</value>
                </string>
                <int>
                    <values>1</values>
                    <values>2</values>
                </int>
            </to>
        </path>
    </root>
    """
--> Ok { string = "SomeString", integers = [ 1, 2 ] }

Pipeline Decoder compositions

We have map, map2 and variants, though the Pipeline style is also possible:

pipelineDecoder : Decoder Data
pipelineDecoder =
    succeed Data
        |> requiredPath [ "path", "to", "string", "value" ] (single string)
        |> requiredPath [ "path", "to", "int", "values" ] (list int)

Development

Globally install Elm Platform, elm-test, and elm-verify-examples

$ elm-test
$ elm-verify-examples
$ elm-verify-examples --elm-test=elm-test # Explicitly set elm-test to use, if particular elm-test version has some issues

Benchmark: Are they efficient? Are they fast?

(Not yet updated for Elm 0.19)

Benchmark codes can be found in benchmarks/ directory.

In Elm 0.18 (elm-xml-decode 1.x)

Using BrianHicks/elm-benchmark and examples in W3School. Available here as a static web page.

Sample result (on my MacBookPro early 2015):

• CPU: Core i5 2.7GHz
• Mem: DDR3 8GB 1867MHz
• Google Chrome 63.0.3239.84 64bit

jinjor/elm-xml-parser was using elm-tools/parser, which suffered from some performance issues at that time (possibly related to this comment?).

Although decoding part should practically be fast enough (see decode result of note.xml and cd_catalog.xml).

Looking forward to see similar benchmarks from other related works!!

License

BSD-3-Clause