npm package: @shexjs/parser
Description: Shape Expressions Compact Syntax (ShExC) parser.
Author: Eric Prud'hommeaux
Latest version: 1.0.0-alpha.28

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# @shexjs/parser
Parse [ShExC](https://shex.io/shex-semantics/#shexc), return [ShExJ](https://shex.io/shex-semantics/#shexj)

## install

``` shell
npm install --save @shexjs/parser
```

## Quick Start
Invoke from the command line:
``` sh
node -e 'console.log(
  JSON.stringify(require("@shexjs/parser")
    .construct()
    .parse("<http://a.example/S1> { <http://a.example/p1> [1 2] }"), null, 2)
)'
```
The result is a ShExJ expression of the input schema:
``` json
{
  "type": "Schema",
  "shapes": [
    {
      "id": "http://a.example/S1",
      "type": "Shape",
      "expression": {
        "type": "TripleConstraint",
        "predicate": "http://a.example/p1",
        "valueExpr": {
          "type": "NodeConstraint",
          "values": [
            {
              "value": "1",
              "type": "http://www.w3.org/2001/XMLSchema#integer"
            },
            {
              "value": "2",
              "type": "http://www.w3.org/2001/XMLSchema#integer"
            }
          ]
        }
      }
    }
  ]
}
```

## Base IRI
Providing a Base IRI (see [MDN docs for URL](https://developer.mozilla.org/en-US/docs/Web/API/URL)) allows you to parse schemas with relative URLs for e.g. shape and property names:
``` sh
node -e 'console.log(
  JSON.stringify(require("@shexjs/parser")
    .construct("http://a.example/")
    .parse("<S1> { <p1> [1 2] }"), null, 2)
)'
```
``` json
{
  "type": "Schema",
  "shapes": [
    {
      "id": "http://a.example/S1",
      "type": "Shape",
      "expression": {
        "type": "TripleConstraint",
        "predicate": "http://a.example/p1",
        "valueExpr": {
          "type": "NodeConstraint",
          "values": [
            {
              "value": "1",
              "type": "http://www.w3.org/2001/XMLSchema#integer"
            },
            {
              "value": "2",
              "type": "http://www.w3.org/2001/XMLSchema#integer"
            }
          ]
        }
      }
    }
  ]
}
```

## Pre-loaded prefixes
A second parameter to `construct` is a map for prefixes that are not defined in the schema:
``` sh
node -e 'console.log(
  JSON.stringify(require("@shexjs/parser")
    .construct("http://a.example/path/path2/", {v: "http://a.example/vocab#"})
    .parse("BASE <../path3>\nPREFIX : <#>\n<S1> { :p1 [v:v1 v:v2] }"), null, 2)
)'
```
``` json
{
  "type": "Schema",
  "shapes": [
    {
      "id": "http://a.example/path/S1",
      "type": "Shape",
      "expression": {
        "type": "TripleConstraint",
        "predicate": "http://a.example/path/path3#p1",
        "valueExpr": {
          "type": "NodeConstraint",
          "values": [
            "http://a.example/vocab#v1",
            "http://a.example/vocab#v2"
          ]
        }
      }
    }
  ]
}
```

## Index option
The third `construct` parameter is for passing parsing options. One handy one is `index`, which returns the final base (`._base`) and prefix mapping (`._prefixes`) encountered during parsing. The `._index` provides indexes into the ShExJ's labled shape declarations and triple expressions :
``` sh
node -e 'console.log(
  JSON.stringify(require("@shexjs/parser")
    .construct("http://a.example/path/path2/", {v: "http://a.example/vocab#"}, {index:true})
    .parse("BASE <../path3>\nPREFIX : <#>\n<S1> { :p1 [v:v1 v:v2] }"), null, 2)
)'
```
``` json
{
  "type": "Schema",
  "shapes": [
    {
      "id": "http://a.example/path/S1",
      "type": "Shape",
      "expression": {
        "type": "TripleConstraint",
        "predicate": "http://a.example/path/path3#p1",
        "valueExpr": {
          "type": "NodeConstraint",
          "values": [
            "http://a.example/vocab#v1",
            "http://a.example/vocab#v2"
          ]
        }
      }
    }
  ],
  "_base": "http://a.example/path/path3",
  "_prefixes": {
    "": "http://a.example/path/path3#"
  },
  "_index": {
    "shapeExprs": {
      "http://a.example/path/S1": <ref to S1 above>
    },
    "tripleExprs": {}
  }
}
```

# Lerna Monorepo

This repo uses [lerna](https://github.com/lerna/lerna) to manage multiple NPM packages. These packages are located in `packages/*`:

- [`shape-map`](../shape-map#readme) -- a [ShapeMap](https://shexspec.github.io/shape-map/) parser
- [`@shexjs/parser`](../shex-parser#readme) -- parse ShExC into ShExJ
- [`@shexjs/writer`](../shex-writer#readme) -- serialize ShExK as ShExC
- [`@shexjs/term`](../shex-term#readme) -- RDF terms uses in ShEx
- [`@shexjs/util`](../shex-util#readme) -- some utilities for transforming schemas or validation output
- [`@shexjs/visitor`](../shex-visitor#readme) -- a [visitor](https://en.wikipedia.org/wiki/Visitor_pattern) for schemas
- [`@shexjs/validator`](../shex-validator#readme) -- validate nodes in an RDF graph against shapes in a schema
- [`@shexjs/eval-validator-api`](../eval-validator-api#readme) -- API called by [`@shexjs/validator`](../shex-validator#readme) for validating Shapes, with tripleExpressions and EXTENDS etc.
- [`@shexjs/eval-simple-1err`](../eval-simple-1err#readme) -- Implementation of [`@shexjs/eval-validator-api`](../eval-validator-api#readme) which reports only one error.
- [`@shexjs/eval-threaded-nerr`](../eval-threaded-nerr#readme) -- Implementation of [`@shexjs/eval-validator-api`](../eval-validator-api#readme) which exhaustively enumerate combinations of ways the data fails to satisfy a shape's expression.
- [`@shexjs/loader`](../shex-loader#readme) -- an API for loading and using ShEx schemas
- [`@shexjs/node`](../shex-node#readme) -- additional API functionality for a node environment
- [`@shexjs/cli`](../shex-cli#readme) -- a set of command line tools for transformaing and validating with schemas
- [`@shexjs/webapp`](../shex-webapp#readme) -- the shex-simple WEBApp
- [`@shexjs/shape-path-query`](../shex-shape-path-query#readme) -- traverse ShEx schemas with a path language
- [`@shexjs/extension-test`](../extension-test#readme) -- a small language for testing semantic actions in ShEx implementations ([more](http://shex.io/extensions/Test/))
- [`@shexjs/extension-map`](../extension-map#readme) -- an extension for transforming data from one schema to another ([more](http://shex.io/extensions/Map/))
- [`@shexjs/extension-eval`](../extension-eval#readme) -- simple extension which evaluates Javascript semantic action code ([more](http://shex.io/extensions/Eval/))