Allow prefix to be a whitespace/comma separated list of prefixes

This project enables pushing the same image to multiple tags, and with
this feature it can enable pushing the same image to multiple
destinations with multiple tags.

A use case for this is if we want to push to both Docker Hub and Quay.io
for example, then prefix could be `"user/repo,quay.io/user/repo"`.

README.md

@@ -29,7 +29,7 @@ The GitHub action's only output is named `tags` and is a JSON formatted list. Se
 
 ## Optional input parameters
 
-- `prefix`: A string that each returned tag should be prefixed with, for example to tag a Docker container set this to `user/repository:`.
+- `prefix`: A string that each returned tag should be prefixed with, for example to tag a Docker container set this to `user/repository:`. This is allowed to be a comma/whitespace separated list to tag multiple images, for example `user/repository:,quay.io/user/repository:`.
 - `defaultTag`: If the tag output would be empty return this tag instead.
   This can be useful for running a workflow in pull requests where no suitable git references are present.
   `prefix` is _not_ automatically added.

__tests__/main.test.js

@@ -258,7 +258,7 @@ test("No ref use default", async () => {
   expect(tags).toEqual(["default-tag"]);
 });
 
-test("Prefix", async () => {
+test("Single prefix", async () => {
   tagInterceptor.reply(200, [
     {
       name: "0.0.1",
@@ -279,6 +279,36 @@ test("Prefix", async () => {
   ]);
 });
 
+test("Multiple prefix", async () => {
+  tagInterceptor.reply(200, [
+    {
+      name: "0.0.1",
+    },
+  ]);
+  const tags = await calculateTags({
+    token: "TOKEN",
+    owner: "owner",
+    repo: "repo",
+    ref: "refs/tags/0.0.1",
+    // test use of different whitespace separators and a combination of both
+    prefix: "prefix1:\tprefix2:\n, prefix3:",
+  });
+  expect(tags).toEqual([
+    "prefix1:0.0.1",
+    "prefix2:0.0.1",
+    "prefix3:0.0.1",
+    "prefix1:0.0",
+    "prefix2:0.0",
+    "prefix3:0.0",
+    "prefix1:0",
+    "prefix2:0",
+    "prefix3:0",
+    "prefix1:latest",
+    "prefix2:latest",
+    "prefix3:latest",
+  ]);
+});
+
 test("Branch", async () => {
   const tags = await calculateTags({
     token: "TOKEN",

src/index.js

@@ -25,6 +25,19 @@ function checkAgainstRegex(name, regexAllowed) {
   return re.test(name);
 }
 
+function expandPrefix(prefix, tag) {
+  // Adds one or more prefixes to a tag, where prefix could be a single prefix
+  // or a comma/whitespace separated list of prefixes.
+  if (!prefix) {
+    return [tag];
+  }
+
+  let rv = [];
+  let prefixes = prefix.split(/\s|,/).filter(Boolean);
+  prefixes.forEach((p) => rv.push(`${p}${tag}`));
+  return rv;
+}
+
 async function calculateTags({
   token,
   owner,
@@ -59,7 +72,7 @@ async function calculateTags({
       }
       return [];
     }
-    return [`${prefix}${branch}`];
+    return expandPrefix(prefix, branch);
   }
   if (!ref.startsWith("refs/tags/")) {
     throw new Error(`Not a tag or branch: ${ref}`);
@@ -77,7 +90,7 @@ async function calculateTags({
   });
   if (!supportedPrerelease(current.prerelease)) {
     core.warning(`Tag prerelease ${currentTag} is not supported`);
-    return [`${prefix}${currentTag}`];
+    return expandPrefix(prefix, currentTag);
   }
 
   const octokit = github.getOctokit(token);
@@ -103,7 +116,7 @@ async function calculateTags({
 
   let outputTags = [];
   if (current.prerelease.length) {
-    outputTags.push(`${prefix}${current.version}`);
+    outputTags.push(...expandPrefix(prefix, current.version));
 
     // return without additional output tags if we got an outdated build number
     const similarTags = tags.filter(
@@ -115,26 +128,32 @@ async function calculateTags({
   }
 
   outputTags.push(
-    `${prefix}${current.major}.${current.minor}.${current.patch}`,
+    ...expandPrefix(prefix, `${current.major}.${current.minor}.${current.patch}`),
   );
 
   core.debug(semver.compare(current, tags[0]) >= 0);
   if (
     !tags.length ||
     semver.compare(current.toString().split("-")[0], tags[0]) >= 0
   ) {
-    outputTags.push(`${prefix}${current.major}.${current.minor}`);
-    outputTags.push(`${prefix}${current.major}`);
-    outputTags.push(`${prefix}latest`);
+    outputTags.push(
+      ...expandPrefix(prefix, `${current.major}.${current.minor}`),
+    );
+    outputTags.push(...expandPrefix(prefix, `${current.major}`));
+    outputTags.push(...expandPrefix(prefix, "latest"));
   } else if (
     semver.compare(current.toString().split("-")[0], majorTags[0]) >= 0
   ) {
-    outputTags.push(`${prefix}${current.major}.${current.minor}`);
-    outputTags.push(`${prefix}${current.major}`);
+    outputTags.push(
+      ...expandPrefix(prefix, `${current.major}.${current.minor}`),
+    );
+    outputTags.push(...expandPrefix(prefix, `${current.major}`));
   } else if (
     semver.compare(current.toString().split("-")[0], minorTags[0]) >= 0
   ) {
-    outputTags.push(`${prefix}${current.major}.${current.minor}`);
+    outputTags.push(
+      ...expandPrefix(prefix, `${current.major}.${current.minor}`),
+    );
   }
   core.debug(`outputTags: ${outputTags}`);
   return outputTags;