feat(package): Add tarball property

core/package/__tests__/core-package.test.js

@@ -144,6 +144,18 @@ describe("Package", () => {
     });
   });
 
+  describe("get .tarball", () => {
+    it("generates the destination filename of npm pack output", () => {
+      const pkg = factory({ name: "pack-me", version: "1.2.3" });
+      expect(pkg.tarball).toBe("pack-me-1.2.3.tgz");
+    });
+
+    it("normalizes package scopes", () => {
+      const pkg = factory({ name: "@scoped/pack-me", version: "4.5.6" });
+      expect(pkg.tarball).toBe("scoped-pack-me-4.5.6.tgz");
+    });
+  });
+
   describe(".toJSON()", () => {
     it("should return clone of internal package for serialization", () => {
       const json = {

core/package/index.js

@@ -8,6 +8,17 @@ function binSafeName({ name, scope }) {
   return scope ? name.substring(scope.length + 1) : name;
 }
 
+function packedFileName(pkg) {
+  // copied almost verbatim from https://git.io/fNobb
+  const name =
+    pkg.name[0] === "@"
+      ? // scoped packages get special treatment
+        pkg.name.substr(1).replace(/\//g, "-")
+      : pkg.name;
+
+  return `${name}-${pkg.version}.tgz`;
+}
+
 // package.json files are not that complicated, so this is intentionally naïve
 function shallowCopy(json) {
   return Object.keys(json).reduce((obj, key) => {
@@ -116,6 +127,12 @@ class Package {
       serialize: {
         value: () => writePkg(this.manifestLocation, pkg),
       },
+      // compute result of `npm pack` filename
+      tarball: {
+        get() {
+          return packedFileName(pkg);
+        },
+      },
     });
   }