Fix fingerprint formation for unit driver tests

Author: David Ungar

unittests/Driver/FineGrainedDependencyGraphTests.cpp

@@ -57,6 +57,19 @@ static bool contains(const Range &range, const T &value) {
          std::end(range);
 }
 
+/// Ensure that 0 and 10 get distinct fingerprints
+TEST(ModuleDepGraph, FingerprintFormation) {
+  ModuleDepGraph graph;
+
+  simulateLoad(graph, &job0, {{NodeKind::topLevel, {"a"}}});
+  simulateLoad(graph, &job1, {{NodeKind::topLevel, {"a->", "z"}}});
+  simulateLoad(graph, &job10, {{NodeKind::topLevel, {"z"}}});
+  {
+    auto jobs = graph.findJobsToRecompileWhenWholeJobChanges(&job0);
+    EXPECT_FALSE(contains(jobs, &job10));
+  }
+}
+
 TEST(ModuleDepGraph, BasicLoad) {
   ModuleDepGraph graph;
 

unittests/Driver/MockingFineGrainedDependencyGraphs.cpp

@@ -43,7 +43,8 @@ mocking_fine_grained_dependency_graphs::getChangesForSimulatedLoad(
   auto swiftDeps =
     cmd->getOutput().getAdditionalOutputForType(file_types::TY_SwiftDeps).str();
   assert(!swiftDeps.empty());
-  swiftDeps.resize(Fingerprint::DIGEST_LENGTH, 'X');
+  // Insert at start so that "1" and "10" are distinct
+  swiftDeps.insert(0, Fingerprint::DIGEST_LENGTH - swiftDeps.size(), '0');
   auto swiftDepsFingerprint = Fingerprint::fromString(swiftDeps);
   if (!swiftDepsFingerprint) {
     llvm::errs() << "unconvertable fingerprint from switdeps ':"