Syntax for snapshot assertions

packages/syntax/src/generators.js

@@ -52,6 +52,10 @@ export function FieldDeclarationStatement(node) {
 export function AssertionEndpointStatement(node) {
   this.word("assert");
   this.space();
+  if (!node.isDynamic) {
+    this.word(":snapshot");
+    this.space();
+  }
   this.print(node.template, node);
   if (node.test) {
     this.space();

packages/syntax/src/parser.js

@@ -94,6 +94,7 @@ export default class SyndicateParser extends _original_Parser {
               if (this.isContextual("assert")) {
                 this.next();
                 const node = this.startNode();
+                node.isDynamic = this.parseMaybeSnapshot();
                 node.template = this.parseExpression();
                 if (this.eatContextual("when")) {
                   this.expect(tt.parenL);

packages/syntax/src/plugin.js

@@ -335,17 +335,19 @@ export default declare((api, options) => {
         if (node.test) {
           path.replaceWith(template(`DATASPACE._currentFacet.addEndpoint(function () {
                                        return (TEST) ? [TEMPLATE, null] : [void 0, null];
-                                     });`)({
+                                     }, ISDYNAMIC);`)({
                                        DATASPACE: state.DataspaceID,
                                        TEST: node.test,
                                        TEMPLATE: node.template,
+                                       ISDYNAMIC: t.booleanLiteral(node.isDynamic),
                                      }));
         } else {
           path.replaceWith(template(`DATASPACE._currentFacet.addEndpoint(function () {
                                        return [TEMPLATE, null];
-                                     });`)({
+                                     }, ISDYNAMIC);`)({
                                        DATASPACE: state.DataspaceID,
                                        TEMPLATE: node.template,
+                                       ISDYNAMIC: t.booleanLiteral(node.isDynamic),
                                      }));
         }
       },

packages/syntax/src/types.js

@@ -61,10 +61,13 @@ defineType("FieldDeclarationStatement", {
 });
 
 defineType("AssertionEndpointStatement", {
-  builder: ["template", "test"],
+  builder: ["isDynamic", "template", "test"],
-  visitor: ["template", "test"],
+  visitor: ["isDynamic", "template", "test"],
   aliases: ["Statement"],
   fields: {
+    isDynamic: {
+      validate: assertOneOf(true, false),
+    },
     template: {
       validate: assertNodeType("Expression"),
     },