Make observe pass options to sample (#794)

* Make observe pass options to sample

* Add test for observe parameters

src/header.js

@@ -94,17 +94,17 @@ module.exports = function(env) {
   // If observation value is given then factor accordingly,
   // otherwise sample a new value.
   // The value is passed to the continuation.
-  env.observe = function(s, k, a, dist, val) {
+  env.observe = function(s, k, a, dist, val, options) {
     if (typeof env.coroutine.observe === 'function') {
-      return env.coroutine.observe(s, k, a, dist, val);
+      return env.coroutine.observe(s, k, a, dist, val, options);
     } else {
       if (val !== undefined) {
         var factorK = function(s) {
           return k(s, val);
         };
         return env.factor(s, factorK, a, dist.score(val));
       } else {
-        return env.sample(s, k, a, dist);
+        return env.sample(s, k, a, dist, options);
       }
     }
   };

src/inference/dream/sample.js

@@ -74,7 +74,7 @@ module.exports = function(env) {
       throw new Error('dream: factor not supported, use observe instead.');
     },
 
-    observe: function(s, k, a, dist) {
+    observe: function(s, k, a, dist, options) {
       if (!this.insideMapData) {
         throw new Error('dream: observe can only be used within mapData with this estimator.');
       }

tests/test-data/deterministic/expected/observeParams.json

@@ -0,0 +1,3 @@
+{
+  "result": "ok"
+}

tests/test-data/deterministic/models/observeParams.wppl

@@ -0,0 +1,6 @@
+sample(Infer({ method: 'forward', samples: 1, guide: true, model: function() {
+  return observe(
+      Discrete({ ps: [1] }),
+      undefined,
+      { guide: function() { return Delta({ v: 'ok' }); }});
+}}));