Follow up from https://github.com/garronej/github_actions_toolkit

src/get_package_json_version.ts

@@ -0,0 +1,61 @@
+
+import fetch from "node-fetch";
+const urlJoin: typeof import("path").join = require("url-join");
+import { setOutputFactory } from "./outputHelper";
+import { NpmModuleVersion } from "./tools/NpmModuleVersion";
+
+import { getActionParamsFactory } from "./inputHelper";
+
+export const { getActionParams } = getActionParamsFactory({
+    "inputNameSubset": [
+        "owner",
+        "repo",
+        "branch",
+        "compare_to_version"
+    ] as const
+});
+
+export type Params = ReturnType<typeof getActionParams>;
+
+type CoreLike = {
+    debug: (message: string) => void;
+};
+
+export const { setOutput } = setOutputFactory<"version" | "compare_result">();
+
+export async function action(
+    _actionName: "get_package_json_version",
+    params: Params,
+    core: CoreLike
+): Promise<Parameters<typeof setOutput>[0]> {
+
+    core.debug(JSON.stringify(params));
+
+    const { owner, repo, branch, compare_to_version } = params;
+
+    const version = await fetch(
+        urlJoin(
+            "https://raw.github.com",
+            owner,
+            repo,
+            branch,
+            "package.json"
+        )
+    )
+        .then(res => res.text())
+        .then(text => JSON.parse(text))
+        .then(({ version }) => version as string)
+        .catch(() => "")
+        ;
+
+    core.debug(`Version on ${owner}/${repo}#${branch} is ${version}`);
+
+    return { 
+        version,
+        "compare_result": NpmModuleVersion.compare(
+        NpmModuleVersion.parse(version || "0.0.0"), 
+        NpmModuleVersion.parse(compare_to_version)
+    ).toString()
+    };
+
+}