elm-xml-decode

XML decoder, sharing the spirit of Json.Decode. Ready for Elm 0.19.

Using miniBill/elm-xml-parser as its parser component, which is based on elm/parser.

Related Works

eeue56/elm-xml was an existing full-package XML parser/decoder for Elm, though I intended 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

Install reasonably new Node.js (currently Node.js 20 is tested)

npm install
npm test

Benchmarks

Benchmark app can be found in benchmarks/ directory. Using examples in W3School and elm-explorations/benchmark.

npm run generate-benchmark
# Open docs/index.html

Also available at https://ymtszw.github.io/elm-xml-decode/

It may hang for a while during JIT warming up, but keep waiting (~ a minute).

Elm 0.19.1, elm-xml-decode 3.2.1

Sample result (on my Windows 10 machine):

Environment
- CPU: Intel Core i7-8700K @ 3.7GHz
- Mem: 64GB
- Windows 10 Pro, 10.0.19044
- Google Chrome 98.0.4758.82 64bit
Versions
- elm 0.19.1
- elm-xml-decode version: 3.2.1
- elm-benchmark 1.0.2