enable multi variable expansion + tests (#2495)

* enable multi var parsing + tests

* formatting violation fix

Author: divmeh-aws

smithy-build/src/main/java/software/amazon/smithy/build/model/SmithyBuildUtils.java

@@ -69,7 +69,7 @@ static ObjectNode expandNode(Node node) {
      */
     private static final class VariableExpander extends NodeVisitor.Default<Node> {
 
-        private static final Pattern INLINE = Pattern.compile("(?:^|[^\\\\])\\$\\{(.+)}");
+        private static final Pattern INLINE = Pattern.compile("(?:^|[^\\\\])\\$\\{([^}]+)}");
         private static final Pattern ESCAPED_INLINE = Pattern.compile("\\\\\\$");
 
         @Override

smithy-build/src/test/java/software/amazon/smithy/build/model/SmithyBuildConfigTest.java

@@ -123,7 +123,8 @@ public void expandsEnvironmentVariables() {
         // Did the array and string values in it expand?
         assertThat(transform.getArgs(),
                 equalTo(Node.objectNode()
-                        .withMember("tags", Node.fromStrings("Hi", "compoundTagFromEnv", "${BAZ}"))));
+                        .withMember("tags",
+                                Node.fromStrings("Hi", "compoundTagFromEnv", "HiAndTagFromEnv", "${BAZ}"))));
     }
 
     @Test

smithy-build/src/test/resources/software/amazon/smithy/build/config-with-env.json

@@ -9,6 +9,7 @@
             "tags": [
               "${FOO}",
               "compound${BAR}",
+              "${FOO}And${BAR}",
               "\\${BAZ}"
             ]
           }