Converting an Output to a string or JSON now produces a warning . (#2496)

CHANGELOG.md

@@ -2,6 +2,11 @@
 
 ### Improvements
 
+- Attempting to convert an [Output<T>] to a string or to JSON will now result in a warning
+  message being printed, as well as information on how to rectify the situation.  This is
+  to help with diagnosing cryptic problems that can occur when Outputs are accidentally
+  concatenated into a string in some part of the program.
+
 ## 0.16.17 (Released February 27th, 2019)
 
 ### Improvements

sdk/nodejs/output.ts

@@ -12,6 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+import * as log from "./log";
 import { Resource } from "./resource";
 import * as runtime from "./runtime";
 
@@ -94,6 +95,38 @@ export class Output<T> {
      */
     public readonly get: () => T;
 
+    /**
+     * [toString] on an [Output<T>] is not supported.  This is because the value an [Output] points
+     * to is asynchronously computed (and thus, this is akin to calling [toString] on a [Promise]).
+     *
+     * Calling this will simply return useful text about the issue, and will log a warning. In a
+     * future version of `@pulumi/pulumi` this will be changed to throw an error when this occurs.
+     *
+     * To get the value of an Output<T> as an Output<string> consider either:
+     * 1. `o.apply(v => ``prefix${v}suffix``)` or
+     * 2. `pulumi.interpolate ``prefix${v}suffix`` `
+     *
+     * This will return an Output with the inner computed value and all resources still tracked. See
+     * https://pulumi.io/help/outputs for more details
+     */
+    /** @internal */ public toString: () => string;
+
+    /**
+     * [toJSON] on an [Output<T>] is not supported.  This is because the value an [Output] points
+     * to is asynchronously computed (and thus, this is akin to calling [toJSON] on a [Promise]).
+     *
+     * Calling this will simply return useful text about the issue, and will log a warning. In a
+     * future version of `@pulumi/pulumi` this will be changed to throw an error when this occurs.
+     *
+     * To get the value of an Output as a JSON value or JSON string consider either:
+     * 1. `o.apply(v => v.toJSON())` or
+     * 2. `o.apply(v => JSON.stringify(v))`
+     *
+     * This will return an Output with the inner computed value and all resources still tracked.
+     * See https://pulumi.io/help/outputs for more details
+     */
+    /** @internal */ public toJSON: () => any;
+
     // Statics
 
     /**
@@ -118,17 +151,49 @@ export class Output<T> {
             resources: Set<Resource> | Resource[] | Resource, promise: Promise<T>, isKnown: Promise<boolean>) {
         this.isKnown = isKnown;
 
+        let resourcesArray: Resource[];
+
         // Always create a copy so that no one accidentally modifies our Resource list.
         if (Array.isArray(resources)) {
-            this.resources = () => new Set<Resource>(resources);
+            resourcesArray = resources;
         } else if (resources instanceof Set) {
-            this.resources = () => new Set<Resource>(resources);
+            resourcesArray = [...resources];
         } else {
-            this.resources = () => new Set<Resource>([resources]);
+            resourcesArray = [resources];
         }
 
+        this.resources = () => new Set<Resource>(resourcesArray);
         this.promise = () => promise;
 
+        const firstResource = resourcesArray[0];
+        this.toString = () => {
+            const message =
+`Calling [toString] on an [Output<T>] is not supported.
+
+To get the value of an Output<T> as an Output<string> consider either:
+1: o.apply(v => \`prefix\${v}suffix\`)
+2: pulumi.interpolate \`prefix\${v}suffix\`
+
+See https://pulumi.io/help/outputs for more details.
+This function may throw in a future version of @pulumi/pulumi.`;
+            log.warn(message, firstResource);
+            return message;
+        };
+
+        this.toJSON = () => {
+            const message =
+`Calling [toJSON] on an [Output<T>] is not supported.
+
+To get the value of an Output as a JSON value or JSON string consider either:
+    1: o.apply(v => v.toJSON())
+    2: o.apply(v => JSON.stringify(v))
+
+See https://pulumi.io/help/outputs for more details.
+This function may throw in a future version of @pulumi/pulumi.`;
+            log.warn(message, firstResource);
+            return message;
+        };
+
         this.apply = <U>(func: (t: T) => Input<U>) => {
             let innerIsKnownResolve: (val: boolean) => void;
             const innerIsKnown = new Promise<boolean>(resolve => {

sdk/nodejs/runtime/closure/createClosure.ts

@@ -193,6 +193,10 @@ class SerializedOutput<T> implements Output<T> {
     /* @internal */ public isKnown: Promise<boolean>;
     /* @internal */ public readonly promise: () => Promise<T>;
     /* @internal */ public readonly resources: () => Set<resource.Resource>;
+
+    /* @internal */ public readonly toString: () => string;
+    /* @internal */ public readonly toJSON: () => any;
+
     /* @internal */ private readonly value: T;
 
     public constructor(value: T) {

sdk/nodejs/runtime/resource.ts

@@ -65,7 +65,7 @@ export function readResource(res: Resource, t: string, name: string, props: Inpu
     }
 
     const label = `resource:${name}[${t}]#...`;
-    log.debug(`Reading resource: id=${id}, t=${t}, name=${name}`);
+    log.debug(`Reading resource: id=${Output.isInstance(id) ? "Output<T>" : id}, t=${t}, name=${name}`);
 
     const monitor: any = getMonitor();
     const resopAsync = prepareResource(label, res, true, props, opts);

sdk/nodejs/runtime/rpc.ts

@@ -56,14 +56,15 @@ export function transferProperties(onto: Resource, label: string, props: Inputs)
             resolveIsKnown(isKnown);
         };
 
+        const propString = Output.isInstance(props[k]) ? "Output<T>" : `${props[k]}`;
         (<any>onto)[k] = new Output(
             onto,
             debuggablePromise(
                 new Promise<any>(resolve => resolveValue = resolve),
-                `transferProperty(${label}, ${k}, ${props[k]})`),
+                `transferProperty(${label}, ${k}, ${propString})`),
             debuggablePromise(
                 new Promise<boolean>(resolve => resolveIsKnown = resolve),
-                `transferIsStable(${label}, ${k}, ${props[k]})`));
+                `transferIsStable(${label}, ${k}, ${propString})`));
     }
 
     return resolvers;

sdk/nodejs/tests/runtime/tsClosureCases.ts

@@ -5044,10 +5044,10 @@ return function () { typescript.parseCommandLine([""]); };
 
 function 'func': tsClosureCases.js(0,0): captured
   module './bin/index.js' which indirectly referenced
-    function 'debug':(...)
-      module './bin/runtime/settings.js' which indirectly referenced
-        function 'getEngine':(...)
-          module './bin/proto/engine_grpc_pb.js' which indirectly referenced
+    function 'Output':(...)
+      module './bin/log/index.js' which indirectly referenced
+        function 'warn':(...)
+          module './bin/runtime/settings.js' which indirectly referenced
 (...)
 Function code:
 (...)
@@ -5485,7 +5485,7 @@ return function () { console.log(regex); foo(); };
             return;
         }
 
-        // if (test.title !== "Output capture") {
+        // if (test.title !== "Fail to capture non-deployment module due to native code") {
         //     continue;
         // }