fix(npm): Fix NPM_TOKEN usage again (#143)

This is a retake on #130. Although npm/cli#8 claims to have support
for `npm_config_//registry.npmjs.org/:_authToken=` usage, my tests
and the reports on the internet says this still doesn't work, even
with the latest npm (7.0.15 at the time).

The only way to pass the token is to have the `authToken` line in
an `.npmrc` file. The quick&dirty way would have been to create one
in the project directory but that may collide with a potentially
pre-existing project `.npmrc`. Trying to merge these seems more
trouble than it is worth:
https://github.com/actions/setup-node/blob/59e61b89511ed136a0b17773f07c349fa5c01e8b/src/authutil.ts
(even worse as you'd need to revert these changes after the fact)

The "better" solution I found is:

1. Create a temporary file as your npmrc
2. Put the token/registry line there
3. Tell npm to use that file as the user config
4. Use the `npm_config_userconfig` for the above to support yarn too

src/targets/npm.ts

@@ -12,6 +12,8 @@ import {
   BaseArtifactProvider,
   RemoteArtifact,
 } from '../artifact_providers/base';
+import { withTempFile } from '../utils/files';
+import { writeFileSync } from 'fs';
 
 const logger = loggerRaw.withScope('[npm]');
 
@@ -24,6 +26,8 @@ export const YARN_BIN = process.env.YARN_BIN || 'yarn';
 const NPM_MIN_MAJOR = 5;
 const NPM_MIN_MINOR = 6;
 
+const NPM_TOKEN_ENV_VAR = 'NPM_TOKEN';
+
 /** A regular expression used to find the package tarball */
 const DEFAULT_PACKAGE_REGEX = /^.*\d\.\d.*\.tgz$/;
 
@@ -43,6 +47,8 @@ export interface NpmTargetOptions extends TargetConfig {
   useOtp?: boolean;
   /** Do we use Yarn instead of NPM? */
   useYarn: boolean;
+  /** Value of NPM_TOKEN so we can pass it to npm executable */
+  token: string;
 }
 
 /** Options for running the NPM publish command */
@@ -125,8 +131,14 @@ export class NpmTarget extends BaseTarget {
    * Extracts NPM target options from the raw configuration
    */
   protected getNpmConfig(): NpmTargetOptions {
+    const token = process.env.NPM_TOKEN;
+    if (!token) {
+      throw new Error('NPM target: NPM_TOKEN not found in the environment');
+    }
+
     const npmConfig: NpmTargetOptions = {
       useYarn: !!process.env.USE_YARN || !hasExecutable(NPM_BIN),
+      token,
     };
     if (this.config.access) {
       if (Object.values(NpmPackageAccess).includes(this.config.access)) {
@@ -180,21 +192,28 @@ export class NpmTarget extends BaseTarget {
       args.push('--tag=next');
     }
 
-    // Pass OTP if configured
-    const spawnOptions: SpawnOptions = {};
-    if (options.otp) {
-      spawnOptions.env = {
-        ...process.env,
-        NPM_CONFIG_OTP: options.otp,
-      };
-    }
-
-    // The path has to be pushed always as the last arg
-    args.push(path);
-
-    // Disable output buffering because NPM/Yarn can ask us for one-time passwords
-    return spawnProcess(bin, args, spawnOptions, {
-      showStdout: true,
+    return withTempFile(filePath => {
+      // Pass OTP if configured
+      const spawnOptions: SpawnOptions = {};
+      spawnOptions.env = { ...process.env };
+      if (options.otp) {
+        spawnOptions.env.NPM_CONFIG_OTP = options.otp;
+      }
+      spawnOptions.env[NPM_TOKEN_ENV_VAR] = this.npmConfig.token;
+      // NOTE(byk): Use npm_config_userconfig instead of --userconfig for yarn compat
+      spawnOptions.env.npm_config_userconfig = filePath;
+      writeFileSync(
+        filePath,
+        `//registry.npmjs.org/:_authToken=\${${NPM_TOKEN_ENV_VAR}}`
+      );
+
+      // The path has to be pushed always as the last arg
+      args.push(path);
+
+      // Disable output buffering because NPM/Yarn can ask us for one-time passwords
+      return spawnProcess(bin, args, spawnOptions, {
+        showStdout: true,
+      });
     });
   }