Make it possible to get a StackReference output promptly (#2824)

CHANGELOG.md

@@ -2,6 +2,12 @@
 
 - Allow setting backend URL explicitly in `Pulumi.yaml` file
 
+- `StackReference` now has a `.getOutputSync` function to retrieve exported values from an existing
+  stack synchronously.  This can be valuable when creating another stack that wants to base
+  flow-control off of the values of an existing stack (i.e. importing the information about all AZs
+  and basing logic off of that in a new stack). Note: this only works for importing values from
+  Stacks that have not exported `secrets`.
+
 ## 0.17.17 (Released June 12, 2019)
 
 ### Improvements

sdk/nodejs/package.json

@@ -21,7 +21,8 @@
         "source-map-support": "^0.4.16",
         "ts-node": "^7.0.0",
         "typescript": "^3.0.0",
-        "upath": "^1.1.0"
+        "upath": "^1.1.0",
+        "deasync": "^0.1.15"
     },
     "devDependencies": {
         "@types/minimist": "^1.2.0",
@@ -30,6 +31,7 @@
         "@types/normalize-package-data": "^2.4.0",
         "@types/read-package-tree": "^5.2.0",
         "@types/semver": "^5.5.0",
+        "@types/deasync": "^0.1.0",
         "istanbul": "^0.4.5",
         "mocha": "^3.5.0",
         "node-gyp": "^3.6.2",

sdk/nodejs/stackReference.ts

@@ -14,6 +14,7 @@
 
 import { all, Input, Output, output } from "./output";
 import { CustomResource, CustomResourceOptions } from "./resource";
+import { promiseResult } from "./utils";
 
 /**
  * Manages a reference to a Pulumi stack. The referenced stack's outputs are available via the
@@ -56,6 +57,25 @@ export class StackReference extends CustomResource {
     public getOutput(name: Input<string>): Output<any> {
         return all([output(name), this.outputs]).apply(([n, os]) => os[n]);
     }
+
+    /**
+     * Fetches the value promptly of the named stack output.  May return undefined if the value is
+     * not known for some reason.
+     *
+     * This operation is not supported (and will throw) if any exported values of the StackReference
+     * are secrets.
+     *
+     * @param name The name of the stack output to fetch.
+     */
+    public getOutputSync(name: string): any {
+        const out = this.getOutput(name);
+        const isSecret = promiseResult(out.isSecret);
+        if (isSecret) {
+            throw new Error("Cannot call [getOutputSync] if the referenced stack has secret outputs. Use [getOutput] instead.");
+        }
+
+        return promiseResult(out.promise());
+    }
 }
 
 /**

sdk/nodejs/utils.ts

@@ -12,6 +12,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+import * as deasync from "deasync";
+
 /**
  * Common code for doing RTTI typechecks.  RTTI is done by having a boolean property on an object
  * with a special name (like "__resource" or "__asset").  This function checks that the object
@@ -39,3 +41,42 @@ export function hasTrueBooleanMember(obj: any, memberName: string | number | sym
 
     return val === true;
 }
+
+/**
+ * Synchronously blocks until the result of this promise is computed.  If the promise is rejected,
+ * this will throw the error the promise was rejected with.  If this promise does not complete this
+ * will block indefinitely.
+ *
+ * Be very careful with this function.  Only wait on a promise if you are certain it is safe to do
+ * so.
+ *
+ * @internal
+ */
+export function promiseResult<T>(promise: Promise<T>): T {
+    enum State {
+        running,
+        finishedSuccessfully,
+        finishedWithError,
+    }
+
+    let result: T;
+    let error = undefined;
+    let state = <State>State.running;
+
+    promise.then(
+        val => {
+            result = val;
+            state = State.finishedSuccessfully;
+        },
+        err => {
+            error = err;
+            state = State.finishedWithError;
+        });
+
+    deasync.loopWhile(() => state === State.running);
+    if (state === State.finishedWithError) {
+        throw error;
+    }
+
+    return result!;
+}

tests/integration/integration_test.go

@@ -891,6 +891,16 @@ func TestStackReferenceNodeJS(t *testing.T) {
 		Config: map[string]string{
 			"org": os.Getenv("PULUMI_TEST_OWNER"),
 		},
+		EditDirs: []integration.EditDir{
+			{
+				Dir:      "step1",
+				Additive: true,
+			},
+			{
+				Dir:      "step2",
+				Additive: true,
+			},
+		},
 	}
 	integration.ProgramTest(t, opts)
 }

tests/integration/stack_reference/index.ts

@@ -6,3 +6,5 @@ let config = new pulumi.Config();
 let org = config.require("org");
 let slug = `${org}/${pulumi.getProject()}/${pulumi.getStack()}`;
 let a = new pulumi.StackReference(slug);
+
+export const val = ["a", "b"];

tests/integration/stack_reference/step1/index.ts

@@ -0,0 +1,15 @@
+// Copyright 2016-2018, Pulumi Corporation.  All rights reserved.
+
+import * as pulumi from "@pulumi/pulumi";
+
+let config = new pulumi.Config();
+let org = config.require("org");
+let slug = `${org}/${pulumi.getProject()}/${pulumi.getStack()}`;
+let a = new pulumi.StackReference(slug);
+
+const oldVal: string[] = a.getOutputSync("val");
+if (oldVal.length !== 2 || oldVal[0] !== "a" || oldVal[1] !== "b") {
+    throw new Error("Invalid result");
+}
+
+export const val2 = pulumi.secret(["a", "b"]);

tests/integration/stack_reference/step2/index.ts

@@ -0,0 +1,22 @@
+// Copyright 2016-2018, Pulumi Corporation.  All rights reserved.
+
+import * as pulumi from "@pulumi/pulumi";
+
+let config = new pulumi.Config();
+let org = config.require("org");
+let slug = `${org}/${pulumi.getProject()}/${pulumi.getStack()}`;
+let a = new pulumi.StackReference(slug);
+
+let gotError = false;
+try
+{
+    a.getOutputSync("val2");
+}
+catch (err)
+{
+    gotError = true;
+}
+
+if (!gotError) {
+    throw new Error("Expected to get error trying to read secret from stack reference.");
+}