Recursively apply dependencyBuildSettings

For now, only "dflags" is used

changelog/dependency-build-settings.dd

@@ -0,0 +1,18 @@
+Let custom build settings to be defined for dependencies
+
+For example;
+`
+{
+	"description": "A simple vibe.d server application.",
+	"license": "proprietary",
+	"name": "dubtest",
+
+	"dependencies": {
+		"vibe-d": { "version" : "~>0.9.2", "dflags" : ["-preview=in"] }
+	}
+}
+`
+
+`-preview=in` will be applied to `vibe-d` and all of its dependencies.
+Any BuildSettings field can be used, parsing support is present. But,
+for now only, dflags is taken into account when compiling.

source/dub/generators/generator.d

@@ -314,20 +314,45 @@ class ProjectGenerator
 		visited.clear();
 
 		// 1. downwards inherits versions, debugVersions, and inheritable build settings
-		static void configureDependencies(const scope ref TargetInfo ti, TargetInfo[string] targets, size_t level = 0)
+		static void configureDependencies(const scope ref TargetInfo ti, TargetInfo[string] targets,
+											BuildSettings[string] dependBS, size_t level = 0)
 		{
+
+			static void applyForcedSettings(const scope ref BuildSettings forced, ref BuildSettings child) {
+				child.addDFlags(forced.dflags);
+			}
+
 			// do not use `visited` here as dependencies must inherit
 			// configurations from *all* of their parents
 			logDebug("%sConfigure dependencies of %s, deps:%(%s, %)", ' '.repeat(2 * level), ti.pack.name, ti.dependencies);
 			foreach (depname; ti.dependencies)
 			{
+				BuildSettings forcedSettings;
 				auto pti = &targets[depname];
 				mergeFromDependent(ti.buildSettings, pti.buildSettings);
-				configureDependencies(*pti, targets, level + 1);
+
+				if (auto matchedSettings = depname in dependBS)
+					forcedSettings = *matchedSettings;
+				else if (auto matchedSettings = "*" in dependBS)
+					forcedSettings = *matchedSettings;
+
+				applyForcedSettings(forcedSettings, pti.buildSettings);
+				configureDependencies(*pti, targets, ["*" : forcedSettings], level + 1);
 			}
 		}
 
-		configureDependencies(*roottarget, targets);
+		BuildSettings[string] dependencyBuildSettings;
+		foreach (key, value; rootPackage.recipe.buildSettings.dependencyBuildSettings)
+		{
+			BuildSettings buildSettings;
+			if (auto target = key in targets)
+			{
+				value.getPlatformSettings(buildSettings, genSettings.platform, target.pack.path);
+				buildSettings.processVars(m_project, target.pack, buildSettings, genSettings, true);
+				dependencyBuildSettings[key] = buildSettings;
+			}
+		}
+		configureDependencies(*roottarget, targets, dependencyBuildSettings);
 
 		// 2. add Have_dependency_xyz for all direct dependencies of a target
 		// (includes incorporated non-target dependencies and their dependencies)

test/depen-build-settings/.gitignore

@@ -0,0 +1,4 @@
+depend.json
+depend2.json
+depen-build-settings.json
+depen-build-settings

test/depen-build-settings/depend/depend2/dub.json

@@ -0,0 +1,5 @@
+{
+	"targetType": "library",
+	"description": "A minimal D application.",
+	"name": "depend2"
+}

test/depen-build-settings/depend/depend2/source/depend2.d

@@ -0,0 +1,6 @@
+import std.stdio;
+
+extern (C) void depend2_func()
+{
+	writeln("depend2_func");
+}

test/depen-build-settings/depend/dub.json

@@ -0,0 +1,9 @@
+{
+	"targetType": "library",
+	"description": "A minimal D application.",
+	"name": "depend1",
+
+	"dependencies": {
+		"depend2": { "version" : "*" }
+	}
+}

test/depen-build-settings/depend/source/depend.d

@@ -0,0 +1,9 @@
+import std.stdio;
+
+extern (C) void depend2_func();
+
+extern (C) void depend1_func()
+{
+	writeln("depend1_func");
+	depend2_func();
+}

test/depen-build-settings/dub.json

@@ -0,0 +1,8 @@
+{
+	"description": "A minimal D application.",
+	"name": "depen-build-settings",
+
+	"dependencies": {
+		"depend1": { "version" : "*", "dflags" : ["-X"] }
+	}
+}

test/depen-build-settings/dub.selections.json

@@ -0,0 +1,7 @@
+{
+	"fileVersion": 1,
+	"versions": {
+		"depend1": {"path":"depend/"},
+		"depend2": {"path":"depend/depend2/"}
+	}
+}

test/depen-build-settings/source/app.d

@@ -0,0 +1,12 @@
+import std.stdio;
+import std.file;
+
+extern (C) void depend1_func();
+
+void main()
+{
+	writeln("Edit source/app.d to start your project.");
+	depend1_func();
+	assert(exists("depend2.json"));
+	assert(exists("depend.json"));
+}