fix: correct reading of sync-labels input.

Contrary to the assumptions made in the unit tests, core.getInput
always returns a string, and !!'false' is true.

Also updates the unit test to reduce changes of regressions by ensuring
that the mocked getInput returns a string, as it would in production.

Fixes #112

Make sure test catches regressions.

__tests__/main.test.ts

@@ -48,15 +48,20 @@ describe('run', () => {
   });
 
   it('(with sync-labels: true) it deletes preexisting PR labels that no longer match the glob pattern', async () => {
-    let mockInput = {
+    const mockInput: {[key: string]: string} = {
       'repo-token': 'foo',
       'configuration-path': 'bar',
-      'sync-labels': true
+      'sync-labels': 'true'
     };
 
     jest
       .spyOn(core, 'getInput')
       .mockImplementation((name: string, ...opts) => mockInput[name]);
+    jest
+      .spyOn(core, 'getBooleanInput')
+      .mockImplementation(
+        (name: string, ...opts) => mockInput[name] === 'true'
+      );
 
     usingLabelerConfigYaml('only_pdfs.yml');
     mockGitHubResponseChangedFiles('foo.txt');
@@ -79,15 +84,20 @@ describe('run', () => {
   });
 
   it('(with sync-labels: false) it issues no delete calls even when there are preexisting PR labels that no longer match the glob pattern', async () => {
-    let mockInput = {
+    const mockInput: {[key: string]: string} = {
       'repo-token': 'foo',
       'configuration-path': 'bar',
-      'sync-labels': false
+      'sync-labels': 'false'
     };
 
     jest
       .spyOn(core, 'getInput')
       .mockImplementation((name: string, ...opts) => mockInput[name]);
+    jest
+      .spyOn(core, 'getBooleanInput')
+      .mockImplementation(
+        (name: string, ...opts) => mockInput[name] === 'true'
+      );
 
     usingLabelerConfigYaml('only_pdfs.yml');
     mockGitHubResponseChangedFiles('foo.txt');

dist/index.js

@@ -49,7 +49,7 @@ function run() {
         try {
             const token = core.getInput('repo-token', { required: true });
             const configPath = core.getInput('configuration-path', { required: true });
-            const syncLabels = !!core.getInput('sync-labels', { required: false });
+            const syncLabels = core.getBooleanInput('sync-labels', { required: false });
             const prNumber = getPrNumber();
             if (!prNumber) {
                 console.log('Could not get pull request number from context, exiting');

src/labeler.ts

@@ -15,7 +15,7 @@ export async function run() {
   try {
     const token = core.getInput('repo-token', {required: true});
     const configPath = core.getInput('configuration-path', {required: true});
-    const syncLabels = !!core.getInput('sync-labels', {required: false});
+    const syncLabels = core.getBooleanInput('sync-labels');
 
     const prNumber = getPrNumber();
     if (!prNumber) {