Add the when() function to all action types. (#1119)

* Add the when() function to all action types.

* bump version

Author: BenBirt

core/assertion.ts

@@ -209,11 +209,16 @@ export class AssertionContext implements ICommonContext {
     this.assertion.dependencies(name);
     return "";
   }
+
   public tags(name: string | string[]) {
     this.assertion.tags(name);
     return "";
   }
 
+  public when(cond: boolean, trueCase: string, falseCase: string = "") {
+    return cond ? trueCase : falseCase;
+  }
+
   public apply<T>(value: AContextable<T>): T {
     if (typeof value === "function") {
       return (value as any)(this);

core/operation.ts

@@ -252,6 +252,10 @@ export class OperationContext implements ICommonContext {
     return "";
   }
 
+  public when(cond: boolean, trueCase: string, falseCase: string = "") {
+    return cond ? trueCase : falseCase;
+  }
+
   public apply<T>(value: Contextable<ICommonContext, T>): T {
     if (typeof value === "function") {
       return (value as any)(this);

version.bzl

@@ -1,3 +1,3 @@
 # NOTE: If you change the format of this line, you must change the bash command
 # in /scripts/publish to extract the version string correctly.
-DF_VERSION = "1.16.3"
+DF_VERSION = "1.16.4"