fix: remove injected sbt script only if it exists

The library was missing a check if the sbt script was injected
successfully. In case it wasn't it failed to remove it because
of a missing cleanup callback.

This patch set refactors the code to handle that case properly.

lib/index.ts

@@ -13,6 +13,11 @@ import * as types from './types';
 import * as tmp from 'tmp';
 tmp.setGracefulCleanup();
 
+interface InjectedScript {
+  path: string;
+  remove: () => void;
+}
+
 const packageFormatVersion = 'mvn:0.0.1';
 const sbtCoursierPluginName = 'sbt-coursier';
 const sbtDependencyGraphPluginName = 'sbt-dependency-graph';
@@ -92,9 +97,7 @@ async function legacyInspect(root: string, targetFile: string, options: any) {
   }
 }
 
-async function getInjectedScriptPath(sbtPluginPath: string, targetFilePath: string):
-    Promise<{injectedScripPath: string, cleanupCallback?: () => void}> {
-
+async function injectSbtScript(sbtPluginPath: string, targetFilePath: string): Promise<InjectedScript> {
   try {
     // We could be running from a bundled CLI generated by `pkg`.
     // The Node filesystem in that case is not real: https://github.com/zeit/pkg#snapshot-filesystem
@@ -104,7 +107,7 @@ async function getInjectedScriptPath(sbtPluginPath: string, targetFilePath: stri
       dir: path.resolve(targetFilePath, 'project/'),
     });
     fs.createReadStream(sbtPluginPath).pipe(fs.createWriteStream(tmpSbtPlugin.name));
-    return { injectedScripPath: tmpSbtPlugin.name, cleanupCallback: tmpSbtPlugin.removeCallback };
+    return { path: tmpSbtPlugin.name, remove: tmpSbtPlugin.removeCallback };
   } catch (error) {
     error.message = error.message + '\n\n' +
         'Failed to create a temporary file to host Snyk script for SBT build analysis.';
@@ -128,14 +131,8 @@ function generateSbtPluginPath(sbtVersion: string): string {
   }
 }
 
-function removeTmpInjectedScript(injectedScripPath) {
-  if (injectedScripPath.cleanupCallback) {
-    injectedScripPath.cleanupCallback();
-  }
-}
-
 async function pluginInspect(root: string, targetFile: string, options: any): Promise<types.PluginResult | null> {
-  let injectedScripPathPromise;
+  let injectedScript: InjectedScript | undefined;
   try {
     const targetFilePath = path.dirname(path.resolve(root, targetFile));
     const sbtArgs = buildArgs(options.args, false, true);
@@ -144,8 +141,8 @@ async function pluginInspect(root: string, targetFile: string, options: any): Pr
     const packageName = path.basename(root);
     const packageVersion = '1.0.0';
 
-    injectedScripPathPromise = await getInjectedScriptPath(sbtPluginPath, targetFilePath);
-    debug('injectedScripPath: ' + injectedScripPathPromise.injectedScripPath);
+    injectedScript = await injectSbtScript(sbtPluginPath, targetFilePath);
+    debug('injectedScript.path: ' + injectedScript.path);
     const stdout = await subProcess.execute('sbt', sbtArgs, {cwd: targetFilePath});
     return {
       plugin: {
@@ -160,7 +157,9 @@ async function pluginInspect(root: string, targetFile: string, options: any): Pr
   } finally {
     // in case of subProcess.execute failing, perform cleanup here, as putting it after `getInjectScriptPath` might
     // not be executed because of `sbt` failing
-    removeTmpInjectedScript(injectedScripPathPromise);
+    if (injectedScript) {
+      injectedScript.remove();
+    }
   }
 }