openapi-merger

Yet another CLI tool for merging multiple OpenAPI files into a single file.

Features

Similar to swagger-merger
Convert all remote & URL refs into local refs
- This is useful on code generation, because it helps openapi-generator to output unique model classes without duplication.
$include keyword: same as $ref, except it merges the object with sibling elements. ($ref ignores them)

Usage

$ npm install -g openapi-merger
$ openapi-merger -i openapi.yaml -o merged.yaml

$include keyword

openapi-merger introduces the special keyword $include. It has similar syntax as $ref, which takes JSON reference as its value.

$include: 'reference to content'

The biggest difference is that $include replaces itself directly by the referenced content, allowing to merge its sibling elements.

Merge objects & arrays

If $include is used in an object and then referenced content is an object too, they are merged.

main.yml

object:
  $include: object.yml
  key3: val3

object.yml

key1: val1
key2: val2

results in:

object:
  key1: val1
  key2: val2
  key3: val3

Arrays go in the same manner.

main.yml

array:
  - $include: array.yml
  - val3

array.yml

- val1
- val2

results in:

array:
  - val1
  - val2
  - val3

If you want not to merge arrays, use $include in a nested array.

main.yml

array:
  - - $include: array.yml
  - val3

array.yml

- val1
- val2

results in:

array:
  - - val1
    - val2
  - val3

Multiple $include at same place

$include can be used multiple times in the same place by appending # with some ID, avoiding key duplication.

$include#foo: ./foo.yml
$include#bar: ./bar.yml

Key modification & Filtering

$include is capable of modification and filtering of the keys of the referenced content. This is useful when you want to aggregate multiple OpenAPI documents of backend services into one for API Gateway.

To utilize this function, a configuration file should be given by -c option. The configuration file is like following:

include:
  # 'foo' class, which add '/v1' prefix to each key
  foo:
    prefix: /v1
  # 'bar' class, which selects only keys matching to regex 
  # here excluding paths that begins 'internal'
  bar: 
    filter: ^(?!/internal).*

Use defined class as following:

main.yml

# using foo class
$include.foo: paths.yml 
# using bar class
$include.bar: paths.yml

paths.yml

/users:
  post:
    ...

/users/{id}:
  get:
    ...

/internal/pets:
  post:
    ...

results in:

# from $include.foo
/v1/users:
  post:
    ...

/v1/users/{id}:
  get:
    ...

/v1/internal/pets:
  post:
    ...

# from $include.bar
/users:
  post:
    ...

/users/{id}:
  get:
    ...

You can still use # notation to avoid key conflicts like below.

$include#a.foo: paths1.yml
$include#b.foo: paths2.yml