Macho DSL is used as engine in AccessPolicy and Subscription​

Definition

Matcho DSL definition:

• If pattern (match) is object, search for inclusion of this object into subject. For example: {x: 1} matches {x: 1, y: 2 ....}. This algorithm is recursive — {a: {b: 5}} matches {a: {b: 5, ...}...}

• Objects with one $enum, $one-of or $contains keys are special cases:

  • $enum — test subject is equal to one of items in the enumeration. {request-method: {$enum: ['get','post']}} matches {request-method: 'post'}

  • $contains — **if a subject is a collection, then search at least one match. {type: {$contains: {system: 'loinc'}} matches {type: [{system: 'snomed'}, {system: 'loinc'}]}

  • $one-of — try to match one of patterns. {a: {$one-of: [{b: present?}, {c: present?}]} matches {a: {c: 5}}

• For array, match the first item in the pattern with the first item in the subject. [1,2] matches [1,2,3...]

• Primitive values (strings, numbers and booleans) are compared by value

• If a string starts with '#' — it will be transformed into regex and matched as regex. {a: '#\\d+'} matches {a: '2345'}

• If a string starts with '.' — it's interpreted as a pointer to another path in the subject to compare. For example: {params: {user_id: '.user.id'}} matches {user: {id: 1}, params: {user_id: 1}}, i.e. user.id == param.user_id

• There are several special string literals postfixed with the ?

  • present? — matches the subject if it is not null, i.e. {a: 'present?'} matches {a: 5} or {a: {b: 6}}

  • nil? — matches if nil/null — {a: nil?} matches {b: 6}

  • not-blank? — matches not blank string.

Debug endpoint

POST /$matcho is a REST endpoint to test matcho engine, which is used in AccessPolicy and Subscriptions.

POST /$matcho
​
matcho: {'a': 1}
resource: {'a': 2}
context: { user: 'u-1' }
​
-- 
​
matcho: {a: 1}
resource: {a: 2}
result:
- expected: 1
  but: 2
  path: [a]