Merge pull request #21 in LFOR/fhirpath.js from bugfix/LF-1606/undefi…

…ned-variables to master

* commit 'eac78a13135769e8cdca63489940fce0ee82007e':
  null value in environment variable is treated as empty
  Environment variable missing check changed
  Fix handling of undefined variables
  Bump websocket-extensions from 0.1.3 to 0.1.4 in /demo

CHANGELOG.md

@@ -3,6 +3,11 @@
 This log documents significant changes for each release. This project follows
 [Semantic Versioning](http://semver.org/).
 
+## [2.7.1] - 2020-10-29
+### Fixed
+- Now, attempting to access an undefined environment variable will result
+ in an error
+
 ## [2.7.0] - 2020-10-21
 ### Added
 - Evaluating expression for a part of a resource

package.json

@@ -1,6 +1,6 @@
 {
  "name": "fhirpath",
- "version": "2.7.0",
+ "version": "2.7.1",
  "description": "A FHIRPath engine",
  "main": "src/fhirpath.js",
  "dependencies": {

src/fhirpath.js

@@ -214,9 +214,16 @@ engine.ExternalConstantTerm = function(ctx, parentData, node) {
  var identifier = extConstant.children[0];
  var varName = engine.Identifier(ctx, parentData, identifier)[0];
  var value = ctx.vars[varName];
+ if (!(varName in ctx.vars)) {
+ throw new Error(
+ "Attempting to access an undefined environment variable: " + varName
+ );
+ }
  // For convenience, we all variable values to be passed in without their array
  // wrapper. However, when evaluating, we need to put the array back in.
- return value === undefined ? [] : value instanceof Array ? value : [value];
+ return value === undefined || value === null
+ ? []
+ : value instanceof Array ? value : [value];
 };
 
 engine.LiteralTerm = function(ctx, parentData, node) {

test/cases/8_variables.yaml

@@ -18,6 +18,19 @@ tests:
  variables:
  a: 5
  result: [4]
+ - desc: 'Empty variable'
+ expression: '%a'
+ variables:
+ a: []
+ result: []
+ - desc: 'Null variable'
+ expression: '%a'
+ variables:
+ a: null
+ result: []
+ - desc: 'Undefined variable'
+ expression: '%a'
+ error: true
  - desc: 'Escaped variables'
  expression: '%`a.b() - 1` - 2'
  variables: