From a72fe5dd8e82ffdaba971891fef5b6dc7cc35002 Mon Sep 17 00:00:00 2001
From: Ryan Cavanaugh <RyanCavanaugh@users.noreply.github.com>
Date: Mon, 18 Jun 2018 16:44:25 -0700
Subject: [PATCH] Add a testcase

---
 src/testRunner/unittests/tsbuild.ts             | 17 +++++++++++++++++
 .../projects/outfile-concat/first/tsconfig.json |  5 +++++
 .../projects/outfile-concat/third/tsconfig.json |  3 +++
 3 files changed, 25 insertions(+)

diff --git a/src/testRunner/unittests/tsbuild.ts b/src/testRunner/unittests/tsbuild.ts
index 2ae034ff673..bd40c7297d9 100644
--- a/src/testRunner/unittests/tsbuild.ts
+++ b/src/testRunner/unittests/tsbuild.ts
@@ -259,6 +259,23 @@ namespace ts {
                 });
             });
         });
+
+        describe("tsbuild - downstream prepend projects always get rebuilt", () => {
+            const fs = outFileFs.shadow();
+            const host = new fakes.CompilerHost(fs);
+            const builder = createSolutionBuilder(host, buildHost, ["/src/third"], { dry: false, force: false, verbose: false });
+            clearDiagnostics();
+            builder.buildAllProjects();
+            assertDiagnosticMessages(/*none*/);
+            assert.equal(fs.statSync("src/third/thirdjs/output/third-output.js").mtimeMs, time(), "First build timestamp is correct");
+            tick();
+            replaceText(fs, "src/first/first_PART1.ts", "Hello", "Hola");
+            tick();
+            builder.resetBuildContext();
+            builder.buildAllProjects();
+            assertDiagnosticMessages(/*none*/);
+            assert.equal(fs.statSync("src/third/thirdjs/output/third-output.js").mtimeMs, time(), "Second build timestamp is correct");
+        });
     }
 
     describe("tsbuild - graph-ordering", () => {
diff --git a/tests/projects/outfile-concat/first/tsconfig.json b/tests/projects/outfile-concat/first/tsconfig.json
index 8370f6512b8..f71a8182585 100644
--- a/tests/projects/outfile-concat/first/tsconfig.json
+++ b/tests/projects/outfile-concat/first/tsconfig.json
@@ -9,6 +9,11 @@
     "declaration": true,
     "outFile": "./bin/first-output.js"
   },
+  "files": [
+    "first_PART1.ts",
+    "first_part2.ts",
+    "first_part3.ts"
+  ],
   "references": [
   ]
 }
diff --git a/tests/projects/outfile-concat/third/tsconfig.json b/tests/projects/outfile-concat/third/tsconfig.json
index 18c98608db1..fef85ce8927 100644
--- a/tests/projects/outfile-concat/third/tsconfig.json
+++ b/tests/projects/outfile-concat/third/tsconfig.json
@@ -9,6 +9,9 @@
     "declaration": true,
     "outFile": "./thirdjs/output/third-output.js"
   },
+  "files": [
+    "third_part1.ts"
+  ],
   "references": [
     { "path": "../first", "prepend": true },
     { "path": "../second", "prepend": true },