Change processSerializedCode func to receive error as 1st arg

Summary:
Since example code of [How to run Prepack](https://github.com/facebook/prepack#how-to-run-prepack) doesn't work(https://github.com/facebook/prepack/issues/781 )
I fixed `processSerializedCode` function to handle error as 1st argument
which follows 'error first callback' convention.
And to verify the changes I've added test code for the case of `StdIn`
Closes https://github.com/facebook/prepack/pull/784

Differential Revision: D5375275

Pulled By: NTillmann

fbshipit-source-id: ea85d0f30db4305aa7fcb5b69bf28f5998a84962

circle.yml

@@ -23,6 +23,7 @@ test:
     - yarn test-serializer-with-coverage
     - yarn test-sourcemaps
     - yarn test-node-cli-mode
+    - yarn test-std-in
     - yarn test-residual
     - yarn test-test262 -- --statusFile $CIRCLE_ARTIFACTS/test262-status.txt --timeout 120 --cpuScale 0.25 --verbose:
         timeout: 1800

package.json

@@ -40,7 +40,8 @@
     "test-error-handler": "babel-node scripts/test-error-handler.js",
     "test-error-handler-with-coverage": "./node_modules/.bin/istanbul cover ./lib/test-error-handler.js --dir coverage.error && ./node_modules/.bin/remap-istanbul -i coverage.error/coverage.json -o coverage-sourcemapped.error -t html",
     "test-node-cli-mode": "bash < scripts/test-node-cli-mode.sh",
-    "test": "npm run test-residual && npm run test-serializer && npm run test-sourcemaps && npm run test-test262 && npm run test-internal && npm run test-error-handler",
+    "test-std-in": "bash < scripts/test-std-in.sh",
+    "test": "npm run test-residual && npm run test-serializer && npm run test-sourcemaps && npm run test-test262 && npm run test-internal && npm run test-error-handler && npm run test-std-in",
     "repl": "node lib/repl-cli.js",
     "prepack": "node lib/prepack-cli.js",
     "prepack-prepack": "node --stack_size=10000 --max_old_space_size=8096 ./bin/prepack.js ./lib/prepack-cli.js --out ./lib/prepack-cli.prepacked.js --compatibility node-cli --mathRandomSeed rnd",

scripts/test-std-in.sh

@@ -0,0 +1,20 @@
+# Prepack test input
+cat ./test/std-in/StdIn.js | node ./bin/prepack.js --out StdIn-test.js
+# Run the resulting program and check it for expected output
+node ./StdIn-test.js | grep "Hello world from std-in!" > /dev/null
+if [[ $? -ne 0 ]]; then
+    exit 1
+fi
+rm ./StdIn-test.js
+
+# Prepack test empty input and check if it logs correct msg
+echo "" | node ./bin/prepack.js --out StdIn-test.js | grep "No source code to prepack" > /dev/null
+if [[ $? -ne 0 ]]; then
+    exit 1
+fi
+
+# Prepack test input and check if it exits with signal 1 
+cat ./test/std-in/StdInError.js | node ./bin/prepack.js --out StdInError-test.js > /dev/null
+if [[ $? -ne 1 ]]; then
+    exit 1
+fi

src/prepack-cli.js

@@ -142,7 +142,7 @@ function run(
       return;
     }
     let serialized = prepackFileSync(inputFilename, resolvedOptions);
-    processSerializedCode(serialized);
+    processSerializedCode(null, serialized);
   } catch (x) {
     console.log(x.message);
     console.log(x.stack);
@@ -159,7 +159,11 @@ function run(
     }
   }
 
-  function processSerializedCode(serialized) {
+  function processSerializedCode(err, serialized) {
+    if (err) {
+      console.error(err);
+      process.exit(1);
+    }
     if (errors.size > 0) {
       console.log("Errors found while prepacking");
       for (let [loc, error] of errors) {
@@ -170,14 +174,20 @@ function run(
       }
       process.exit(1);
     }
-    if (outputFilename) {
-      console.log(`Prepacked source code written to ${outputFilename}.`);
-      fs.writeFileSync(outputFilename, serialized.code);
-    } else {
-      console.log(serialized.code);
-    }
-    if (outputSourceMap) {
-      fs.writeFileSync(outputSourceMap, serialized.map ? JSON.stringify(serialized.map) : "");
+    if (serialized) {
+      if (serialized.code === '') {
+        console.log('No source code to prepack.');
+        return;
+      }
+      if (outputFilename) {
+        console.log(`Prepacked source code written to ${outputFilename}.`);
+        fs.writeFileSync(outputFilename, serialized.code);
+      } else {
+        console.log(serialized.code);
+      }
+      if (outputSourceMap) {
+        fs.writeFileSync(outputSourceMap, serialized.map ? JSON.stringify(serialized.map) : "");
+      }
     }
   }
 

test/std-in/StdIn.js

@@ -0,0 +1,8 @@
+function hello() {
+  return 'Hello';
+}
+function world() {
+  return 'world';
+}
+let greeting = hello() + ' ' + world();
+console.log(greeting + ' from std-in!');

test/std-in/StdInError.js

@@ -0,0 +1,8 @@
+function hello() {
+  return 'Hello';
+}
+function world() {
+  return 'world';
+// SyntaxError: Unexpected token
+let greeting = hello() + ' ' + world();
+console.log(greeting + ' from std-in!');