Adding comparison check for decrementing version

src/action/index.ts

@@ -35,6 +35,11 @@ async function main(): Promise<void> {
         `\n📦 ${results.package} v${results.version} is already published to NPM`
       );
     }
+    else if (options.greaterVersion && results.type === "lower") {
+      console.log(
+        `\n📦 ${results.package} v${results.version} is lower than the version published to NPM`
+      );
+    }
     else if (results.dryRun) {
       console.log(
         `\n📦 ${results.package} v${results.version} was NOT actually published to NPM (dry run)`

src/npm-publish.ts

@@ -18,19 +18,31 @@ export async function npmPublish(opts: Options = {}): Promise<Results> {
   // Determine if/how the version has changed
   let diff = semver.diff(manifest.version, publishedVersion);
 
-  if (diff || !options.checkVersion) {
+  // Compare both versions to see if it's changed
+  let cmp = semver.compare(manifest.version, publishedVersion);
+
+  let shouldPublish =
+    !options.checkVersion ||
+    // compare returns 1 if manifest is higher than published
+    (options.greaterVersion && cmp === 1) ||
+    // compare returns 0 if the manifest is the same as published
+    cmp !== 0;
+
+  if (shouldPublish) {
     // Publish the new version to NPM
     await npm.publish(manifest, options);
   }
 
   let results: Results = {
     package: manifest.name,
-    type: diff || "none",
+    type: (cmp === -1 && "lower") || diff || "none",
     version: manifest.version.raw,
     oldVersion: publishedVersion.raw,
     tag: options.tag,
-    access: options.access || (manifest.name.startsWith("@") ? "restricted" : "public"),
-    dryRun: options.dryRun
+    access:
+      options.access ||
+      (manifest.name.startsWith("@") ? "restricted" : "public"),
+    dryRun: options.dryRun,
   };
 
   options.debug("OUTPUT:", results);

src/results.ts

@@ -10,7 +10,7 @@ export interface Results {
   /**
    * The type of version change that occurred
    */
-  type: ReleaseType | "none";
+  type: ReleaseType | "lower" | "none";
 
   /**
    * The name of the NPM package that was published

test/specs/action/success.spec.js

@@ -123,6 +123,64 @@ describe("GitHub Action - success tests", () => {
     npm.assert.ran(4);
   });
 
+  it("should not publish a new version to NPM if the version is lower and greaterVersion flag is set", () => {
+    files.create([
+      {
+        path: "workspace/package.json",
+        contents: { name: "my-lib", version: "0.1.0" },
+      },
+    ]);
+
+    npm.mock({
+      args: ["config", "get", "userconfig"],
+      stdout: `${paths.npmrc}${EOL}`,
+    });
+
+    npm.mock({
+      args: ["view", "my-lib", "version"],
+      stdout: `1.0.0${EOL}`,
+    });
+
+    npm.mock({
+      args: ["config", "get", "userconfig"],
+      stdout: `${paths.npmrc}${EOL}`,
+    });
+
+    npm.mock({
+      args: ["publish"],
+      env: { INPUT_TOKEN: "my-secret-token" },
+      stdout: `my-lib 0.1.0${EOL}`,
+    });
+
+    let cli = exec.action({
+      env: {
+        INPUT_TOKEN: "my-secret-token",
+        "INPUT_GREATER-VERSION": "true",
+      },
+    });
+
+    expect(cli).to.have.stderr("");
+    expect(cli).stdout.to.include("my-lib 0.1.0");
+    expect(cli).stdout.to.include(
+      "my-lib v0.1.0 is lower than the version published to NPM"
+    );
+    expect(cli).stdout.to.include("::set-output name=type::lower");
+    expect(cli).stdout.to.include("::set-output name=version::0.1.0");
+    expect(cli).stdout.to.include("::set-output name=old-version::1.0.0");
+    expect(cli).stdout.to.include("::set-output name=tag::latest");
+    expect(cli).stdout.to.include("::set-output name=access::public");
+    expect(cli).stdout.to.include("::set-output name=dry-run::false");
+    expect(cli).to.have.exitCode(0);
+
+    files.assert.contents(
+      "home/.npmrc",
+      `//registry.npmjs.org/:_authToken=\${INPUT_TOKEN}${EOL}` +
+        `registry=https://registry.npmjs.org/${EOL}`
+    );
+
+    npm.assert.ran(4);
+  });
+
   it("should publish a new version to NPM if no package exists", async () => {
     files.create([
       {