Merge pull request #718 from marshall007/marshall_713

feat: allowedValue param in const keyword error

README.md

@@ -899,7 +899,7 @@ This allows you to do nice things like the following.
 
 ```javascript
 var validate = new Ajv().addSchema(schema).addFormat(name, regex).getSchema(uri);
-```  
+```
 
 ##### .addMetaSchema(Array<Object>|Object schema [, String key]) -> Ajv
 
@@ -1199,6 +1199,7 @@ Properties of `params` object in errors depend on the keyword that failed valida
 - `patternRequired` (in ajv-keywords) - property `missingPattern` (required pattern that did not match any property).
 - `type` - property `type` (required type(s), a string, can be a comma-separated list)
 - `uniqueItems` - properties `i` and `j` (indices of duplicate items).
+- `const` - property `allowedValue` pointing to the value (the schema of the keyword).
 - `enum` - property `allowedValues` pointing to the array of values (the schema of the keyword).
 - `$ref` - property `ref` with the referenced schema URI.
 - `oneOf` - property `passingSchemas` (array of indices of passing schemas, null if no schema passes).

lib/dot/errors.def

@@ -167,7 +167,7 @@
   additionalItems: "{ limit: {{=$schema.length}} }",
   additionalProperties: "{ additionalProperty: '{{=$additionalProperty}}' }",
   anyOf:           "{}",
-  const:           "{}",
+  const:           "{ allowedValue: schema{{=$lvl}} }",
   contains:        "{}",
   dependencies:    "{ property: '{{= it.util.escapeQuotes($property) }}', missingProperty: '{{=$missingProperty}}', depsCount: {{=$deps.length}}, deps: '{{= it.util.escapeQuotes($deps.length==1 ? $deps[0] : $deps.join(\", \")) }}' }",
   'enum':          "{ allowedValues: schema{{=$lvl}} }",