cache the generated test main file: dub_test_root.d

these changes prevent dub from rebuilding a project every time it runs a unittest.

changelog/cache-generated-test-config.dd

@@ -0,0 +1,4 @@
+Caching of generated unittest runner (dub test)
+
+For projects without a user-defined unittest configuration `dub test` generates a main file automatically.
+This main file is now being cached and won't be regenerated won subsequent runs without file changes.

source/dub/dub.d

@@ -662,6 +662,7 @@ class Dub {
 			}
 
 			// prepare the list of tested modules
+
 			string[] import_modules;
 			foreach (file; lbuildsettings.sourceFiles) {
 				if (file.endsWith(".d")) {
@@ -679,11 +680,23 @@ class Dub {
 				}
 			}
 
+			NativePath mainfile;
+			if (settings.tempBuild)
+				mainfile = getTempFile("dub_test_root", ".d");
+			else {
+				import dub.generators.build : computeBuildName;
+				mainfile = m_project.rootPackage.path ~ format(".dub/code/%s_dub_test_root.d", computeBuildName(test_config, settings, import_modules));
+			}
+
+			mkdirRecurse(mainfile.parentPath.toNativeString());
+
+			bool regenerateMainFile = settings.force || !existsFile(mainfile);
+
 			// generate main file
-			NativePath mainfile = getTempFile("dub_test_root", ".d");
 			tcinfo.sourceFiles[""] ~= mainfile.toNativeString();
 			tcinfo.mainSourceFile = mainfile.toNativeString();
-			if (!m_dryRun) {
+
+			if (!m_dryRun && regenerateMainFile) {
 				auto fil = openFile(mainfile, FileMode.createTrunc);
 				scope(exit) fil.close();
 				fil.write("module dub_test_root;\n");

source/dub/generators/build.d

@@ -32,6 +32,24 @@ string getObjSuffix(const scope ref BuildPlatform platform)
     return platform.platform.canFind("windows") ? ".obj" : ".o";
 }
 
+string computeBuildName(string config, GeneratorSettings settings, const string[][] hashing...)
+{
+	import std.digest;
+	import std.digest.md;
+
+	MD5 hash;
+	hash.start();
+	void addHash(in string[] strings...) { foreach (s; strings) { hash.put(cast(ubyte[])s); hash.put(0); } hash.put(0); }
+	foreach(strings; hashing)
+		addHash(strings);
+	auto hashstr = hash.finish().toHexString().idup;
+
+    return format("%s-%s-%s-%s-%s_%s-%s", config, settings.buildType,
+			settings.platform.platform.join("."),
+			settings.platform.architecture.join("."),
+			settings.platform.compiler, settings.platform.frontendVersion, hashstr);
+}
+
 class BuildGenerator : ProjectGenerator {
 	private {
 		PackageManager m_packageMan;
@@ -329,33 +347,23 @@ class BuildGenerator : ProjectGenerator {
 
 	private string computeBuildID(string config, in BuildSettings buildsettings, GeneratorSettings settings)
 	{
-		import std.digest;
-		import std.digest.md;
-		import std.bitmanip;
-
-		MD5 hash;
-		hash.start();
-		void addHash(in string[] strings...) { foreach (s; strings) { hash.put(cast(ubyte[])s); hash.put(0); } hash.put(0); }
-		void addHashI(int value) { hash.put(nativeToLittleEndian(value)); }
-		addHash(buildsettings.versions);
-		addHash(buildsettings.debugVersions);
-		//addHash(buildsettings.versionLevel);
-		//addHash(buildsettings.debugLevel);
-		addHash(buildsettings.dflags);
-		addHash(buildsettings.lflags);
-		addHash((cast(uint)buildsettings.options).to!string);
-		addHash(buildsettings.stringImportPaths);
-		addHash(buildsettings.importPaths);
-		addHash(settings.platform.architecture);
-		addHash(settings.platform.compilerBinary);
-		addHash(settings.platform.compiler);
-		addHashI(settings.platform.frontendVersion);
-		auto hashstr = hash.finish().toHexString().idup;
-
-		return format("%s-%s-%s-%s-%s_%s-%s", config, settings.buildType,
-			settings.platform.platform.join("."),
-			settings.platform.architecture.join("."),
-			settings.platform.compiler, settings.platform.frontendVersion, hashstr);
+		const(string[])[] hashing = [
+			buildsettings.versions,
+			buildsettings.debugVersions,
+			buildsettings.dflags,
+			buildsettings.lflags,
+			buildsettings.stringImportPaths,
+			buildsettings.importPaths,
+			settings.platform.architecture,
+			[
+				(cast(uint)buildsettings.options).to!string,
+				settings.platform.compilerBinary,
+				settings.platform.compiler,
+				settings.platform.frontendVersion.to!string,
+			],
+		];
+
+		return computeBuildName(config, settings, hashing);
 	}
 
 	private void copyTargetFile(NativePath build_path, BuildSettings buildsettings, GeneratorSettings settings)

test/cache-generated-test-config.sh

@@ -0,0 +1,24 @@
+#!/usr/bin/env bash
+
+. $(dirname "${BASH_SOURCE[0]}")/common.sh
+cd ${CURR_DIR}/cache-generated-test-config
+rm -rf .dub
+
+${DUB} test --compiler=${DC}
+
+STAT="stat -c '%Y'"
+[[ "$OSTYPE" == "darwin"* ]] && STAT="stat -f '%m' -t '%Y'"
+
+EXECUTABLE_TIME="$(${STAT} cache-generated-test-config-test-library)"
+[ -z "$EXECUTABLE_TIME" ] && die $LINENO 'no EXECUTABLE_TIME was found'
+MAIN_TIME="$(${STAT} "$(ls .dub/code/*dub_test_root.d)")"
+[ -z "$MAIN_TIME" ] && die $LINENO 'no MAIN_TIME was found'
+
+${DUB} test --compiler=${DC}
+MAIN_FILES_COUNT=$(ls .dub/code/*dub_test_root.d | wc -l)
+
+[ $MAIN_FILES_COUNT -ne 1 ] && die $LINENO 'DUB generated more then one main file'
+[ "$EXECUTABLE_TIME" != "$(${STAT} cache-generated-test-config-test-library)" ] && die $LINENO 'The executable has been rebuilt'
+[ "$MAIN_TIME" != "$(${STAT} "$(ls .dub/code/*dub_test_root.d | head -n1)")" ] && die $LINENO 'The test main file has been rebuilt'
+
+exit 0

test/cache-generated-test-config/dub.sdl

@@ -0,0 +1,3 @@
+name "cache-generated-test-config"
+
+targetType "staticLibrary"

test/cache-generated-test-config/source/test.d

@@ -0,0 +1,6 @@
+module test;
+
+unittest
+{
+    assert(true);
+}