feat(params): add support for list of expressions as default value (#111)

(a = (doSomething(), doSomethingElse(), true)) => {} is a prefectly valid syntax that is used
extensively by code instrumenters. When a list of expressions is used as a default value, only the
last expression is the actual default value. This commit add support for this syntax.
TAG: latest

fixes #110

Author: Eric MORAND

src/lib/plugins/params.js

@@ -32,9 +32,23 @@ export default (app) => (node, result) => {
     const name = param.name || defaultArgsName || restArgName
 
     result.args.push(name)
-    result.defaults[name] = param.right
-      ? result.value.slice(param.right.start, param.right.end)
-      : undefined
+
+    if (param.right && param.right.type === 'SequenceExpression') {
+      let value
+      let lastExpression = param.right.expressions.pop()
+
+      if (lastExpression.type === 'NullLiteral') {
+        value = null
+      } else {
+        value = lastExpression.value
+      }
+
+      result.defaults[name] = value
+    } else {
+      result.defaults[name] = param.right
+        ? result.value.slice(param.right.start, param.right.end)
+        : undefined
+    }
   })
   result.params = result.args.join(', ')
 

test/index.js

@@ -29,27 +29,39 @@ const actuals = {
     'function (c) {return c * 3}',
     'function (...restArgs) {return 321}',
     'function () {}',
+    'function (a = (true, false)) {}',
+    'function (a = (true, null)) {}',
+    'function (a, b = (i++, true)) {}',
   ],
   named: [
     'function namedFn (a = {foo: "ba)r", baz: 123}, cb, ...restArgs) {return a * 3}',
     'function namedFn (b, callback, ...restArgs) {callback(null, b + 3)}',
     'function namedFn (c) {return c * 3}',
     'function namedFn (...restArgs) {return 321}',
     'function namedFn () {}',
+    'function namedFn(a = (true, false)) {}',
+    'function namedFn(a = (true, null)) {}',
+    'function namedFn(a, b = (i++, true)) {}',
   ],
   generators: [
     'function * namedFn (a = {foo: "ba)r", baz: 123}, cb, ...restArgs) {return a * 3}',
     'function * namedFn (b, callback, ...restArgs) {callback(null, b + 3)}',
     'function * namedFn (c) {return c * 3}',
     'function * namedFn (...restArgs) {return 321}',
     'function * namedFn () {}',
+    'function * namedFn(a = (true, false)) {}',
+    'function * namedFn(a = (true, null)) {}',
+    'function * namedFn(a, b = (i++, true)) {}',
   ],
   arrows: [
     '(a = {foo: "ba)r", baz: 123}, cb, ...restArgs) => {return a * 3}',
     '(b, callback, ...restArgs) => {callback(null, b + 3)}',
     '(c) => {return c * 3}',
     '(...restArgs) => {return 321}',
     '() => {}',
+    '(a = (true, false)) => {}',
+    '(a = (true, null)) => {}',
+    '(a, b = (i++, true)) => {}',
     '(a) => a * 3 * a',
     'd => d * 355 * d',
     'e => {return e + 5235 / e}',
@@ -109,6 +121,27 @@ const regulars = [
     body: '',
     defaults: {},
   },
+  {
+    name: null,
+    params: 'a',
+    args: ['a'],
+    body: '',
+    defaults: {a: false},
+  },
+  {
+    name: null,
+    params: 'a',
+    args: ['a'],
+    body: '',
+    defaults: {a: null},
+  },
+  {
+    name: null,
+    params: 'a, b',
+    args: ['a', 'b'],
+    body: '',
+    defaults: {a: undefined, b: true},
+  },
 ]
 
 /**