openapi-path-templating

Path Templating allow defining values based on information that will only be available within the HTTP message in an actual API call. This mechanism is used by Paths Object of OpenAPI specification.

openapi-path-templating is a parser, validator and resolver for OpenAPI Path Templating. It supports Path Templating defined in following OpenAPI specification versions:

• OpenAPI 2.0
• OpenAPI 3.0.0
• OpenAPI 3.0.1
• OpenAPI 3.0.2
• OpenAPI 3.0.3
• OpenAPI 3.1.0

Table of Contents

• Getting started
  • Installation
  • Usage
    • Extraction
    • Parsing
    • Validation
    • Resolution
    • Grammar
• More about OpenAPI Path Templating
• License

Getting started

Installation

You can install openapi-path-templating using npm:

 $ npm install openapi-path-templating

Usage

openapi-path-templating currently supports parsing, validation and resolution. Both parser and validator are based on a superset of ABNF (SABNF) and use apg-lite parser generator.

Parsing

Parsing a Path template expression is as simple as importing the parse function and calling it.

import { parse } from 'openapi-path-templating';

const parseResult = parse('/pets/{petId}');
parseResult.result.success; // => true

parseResult variable has the following shape:

{
  result: {
    success: true,
    state: 101,
    stateName: 'MATCH',
    length: 13,
    matched: 13,
    maxMatched: 13,
    maxTreeDepth: 18,
    nodeHits: 324
  },
  ast: fnast {
    callbacks: [
      'path-template': [Function: pathTemplate],
      path: [Function: path],
      query: [Function: query],
      'query-marker': [Function: queryMarker],
      fragment: [Function: fragment],
      'fragment-marker': [Function: fragmentMarker],
      slash: [Function: slash],
      'path-literal': [Function: pathLiteral],
      'template-expression': [Function: templateExpression],
      'template-expression-param-name': [Function: templateExpressionParamName]
    ],
    init: [Function (anonymous)],
    ruleDefined: [Function (anonymous)],
    udtDefined: [Function (anonymous)],
    down: [Function (anonymous)],
    up: [Function (anonymous)],
    translate: [Function (anonymous)],
    setLength: [Function (anonymous)],
    getLength: [Function (anonymous)],
    toXml: [Function (anonymous)]
  }
}

Interpreting AST as list of entries

import { parse } from 'openapi-path-templating';

const parseResult = parse('/pets/{petId}');
const parts = [];

parseResult.ast.translate(parts);

After running the above code, parts variable has the following shape:

[
  [ 'path-template', '/pets/{petId}' ],
  [ 'slash', '/' ],
  [ 'path-literal', 'pets' ],
  [ 'slash', '/' ],
  [ 'template-expression', '{petId}' ]
]

Interpreting AST as XML

import { parse } from 'openapi-path-templating';

const parseResult = parse('/pets/{petId}');
const xml = parseResult.ast.toXml();

After running the above code, xml variable has the following content:

<?xml version="1.0" encoding="utf-8"?>
<root nodes="7" characters="13">
  <!-- input string -->
  /pets/{petId}
  <node name="path-template" index="0" length="13">
    /pets/{petId}
    <node name="path" index="0" length="13">
      /pets/{petId}
      <node name="slash" index="0" length="1">
        /
      </node><!-- name="slash" -->
      <node name="path-literal" index="1" length="4">
        pets
      </node><!-- name="path-literal" -->
      <node name="slash" index="5" length="1">
        /
      </node><!-- name="slash" -->
      <node name="template-expression" index="6" length="7">
        {petId}
        <node name="template-expression-param-name" index="7" length="5">
          petId
        </node><!-- name="template-expression-param-name" -->
      </node><!-- name="template-expression" -->
    </node><!-- name="path" -->
  </node><!-- name="path-template" -->
</root>

NOTE: AST can also be traversed in classical way using depth first traversal. For more information about this option please refer to apg-js and apg-js-examples.

Validation

Validating a Path Templating is as simple as importing the test function and calling it.

import { test } from 'openapi-path-templating';

test('/pets/{petId}'); // => true
test('/a{petId}'); // => true
test('/pets'); // => true
test('/pets', { strict: true }); // => false (doesn't contain any template-expression)

Resolution

Resolving a Path Templating is as simple as importing the resolve function and calling it.

import { resolve } from 'openapi-path-templating';

resolve('/pets/{petId}', { petId: 3 }); // => "/pets/3"

Grammar

New grammar instance can be created in following way:

import { Grammar } from 'openapi-path-templating';

const grammar = new Grammar();

To obtain original ABNF (SABNF) grammar as a string:

import { Grammar } from 'openapi-path-templating';

const grammar = new Grammar();

grammar.toString();
// or
String(grammar);

More about OpenAPI Path Templating

The Path Templating is defined by the following ABNF syntax

; OpenAPI Path Templating ABNF syntax
path-template                  = path [ query-marker query ] [ fragment-marker fragment ]
path                           = slash *( path-segment slash ) [ path-segment ]
path-segment                   = 1*( path-literal / template-expression )
query                          = *( query-literal )
query-literal                  = 1*( unreserved / pct-encoded / sub-delims / ":" / "@" / "/" / "?" / "&" / "=" )
query-marker                   = "?"
fragment                       = *( fragment-literal )
fragment-literal               = 1*( unreserved / pct-encoded / sub-delims / ":" / "@" / "/" / "?" )
fragment-marker                = "#"
slash                          = "/"
path-literal                   = 1*( unreserved / pct-encoded / sub-delims-no-slash / ":" / "@" )
template-expression            = "{" template-expression-param-name "}"
template-expression-param-name = 1*( unreserved / pct-encoded / sub-delims-no-slash / ":" / "@" )

; Characters definitions (from RFC 3986)
unreserved          = ALPHA / DIGIT / "-" / "." / "_" / "~"
pct-encoded         = "%" HEXDIG HEXDIG
sub-delims          = "!" / "$" / "&" / "'" / "(" / ")"
                    / "*" / "+" / "," / ";" / "="
sub-delims-no-slash = "!" / "$" / "&" / "'" / "(" / ")"
                    / "*" / "+" / "," / ";"
ALPHA               = %x41-5A / %x61-7A   ; A-Z / a-z
DIGIT               = %x30-39            ; 0-9
HEXDIG              = DIGIT / "A" / "B" / "C" / "D" / "E" / "F"

License

openapi-path-templating is licensed under Apache 2.0 license. openapi-path-templating comes with an explicit NOTICE file containing additional legal notices and information.