[infer][java] When using Buck to analyze Java projects, only report the errors found on the targets passed on the command line

Summary:
Before this diff, Infer was simply going through the list of jar files found in `buck-out` and was loading all the `report.json` files found in those jar files in order to merge them into a final report. The main drawback of this was that removing `buck-out` was mandatory to get accurate results when switching between targets to analyze.

With this diff, we now use the `buck audit classpath` option to get from a list of targets, the list of jar files to load the `report.json` files from. This allows to more easily use Infer from the command line when switch branches from the repositories or when switching between targets to analyze.

Reviewed By: martinoluca

Differential Revision: D3922548

fbshipit-source-id: ec550fa

infer/lib/python/inferlib/bucklib.py

@@ -273,7 +273,16 @@ def load_json_report(opened_jar):
         raise NotFoundInJar
 
 
-def collect_results(args, start_time):
+def get_output_jars(targets):
+    if len(targets) == 0:
+        return []
+    else:
+        audit_output = subprocess.check_output(
+            ['buck', 'audit', 'classpath'] + targets)
+        return audit_output.strip().split('\n')
+
+
+def collect_results(args, start_time, targets):
     """Walks through buck-gen, collects results for the different buck targets
     and stores them in in args.infer_out/results.csv.
     """
@@ -297,9 +306,7 @@ def collect_results(args, start_time):
     expected_analyzer = stats['normal']['analyzer']
     expected_version = stats['normal']['infer_version']
 
-    for root, _, files in os.walk(DEFAULT_BUCK_OUT_GEN):
-        for f in [f for f in files if f.endswith('.jar')]:
-            path = os.path.join(root, f)
+    for path in get_output_jars(targets):
         try:
             with zipfile.ZipFile(path) as jar:
                 # Accumulate integers and float values
@@ -308,8 +315,8 @@ def collect_results(args, start_time):
                 found_analyzer = target_stats['normal']['analyzer']
                 found_version = target_stats['normal']['infer_version']
 
-                    if (found_analyzer != expected_analyzer
-                            or found_version != expected_version):
+                if found_analyzer != expected_analyzer \
+                        or found_version != expected_version:
                     continue
                 else:
                     for type_k in ['int', 'float']:
@@ -459,7 +466,7 @@ class Wrapper:
 
     def _collect_results(self, start_time):
         self.timer.start('Collecting results ...')
-        collect_results(self.infer_args, start_time)
+        collect_results(self.infer_args, start_time, self.normalized_targets)
         self.timer.stop('Done')
 
     def run(self):