Added annotation that can be added to architectures, to mark them as not requiring memory (e.g. to allow assembling MCUs with CPUs configured to those architectures without memory being present). Closes #1201.

src/main/java/li/cil/oc/api/machine/Architecture.java

@@ -148,7 +148,22 @@ public interface Architecture {
      */
     @Retention(RetentionPolicy.RUNTIME)
     @Target(ElementType.TYPE)
-    static @interface Name {
+    @interface Name {
         String value();
     }
+
+    /**
+     * Architectures flagged with this annotation can potentially run without
+     * any additional memory installed in the computer.
+     * <p/>
+     * Use this to allow assembly of devices such as microcontrollers without
+     * any memory being installed in them while your architecture is being
+     * used by the CPU being installed. Note to actually make the machine
+     * start up you only need to always return <tt>true</tt> from
+     * {@link #recomputeMemory}.
+     */
+    @Retention(RetentionPolicy.RUNTIME)
+    @Target(ElementType.TYPE)
+    @interface NoMemoryRequirements {
+    }
 }

src/main/scala/li/cil/oc/common/template/Template.scala

@@ -9,6 +9,7 @@ import li.cil.oc.api.driver.item.Container
 import li.cil.oc.api.driver.item.Inventory
 import li.cil.oc.api.driver.item.Memory
 import li.cil.oc.api.driver.item.Processor
+import li.cil.oc.api.machine.Architecture
 import li.cil.oc.common.Slot
 import li.cil.oc.common.Tier
 import net.minecraft.inventory.IInventory
@@ -40,10 +41,11 @@ abstract class Template {
     val hasCase = caseTier(inventory) != Tier.None
     val hasCPU = this.hasCPU(inventory)
     val hasRAM = this.hasRAM(inventory)
+    val requiresRAM = this.requiresRAM(inventory)
     val complexity = this.complexity(inventory)
     val maxComplexity = this.maxComplexity(inventory)
 
-    val valid = hasCase && hasCPU && hasRAM && complexity <= maxComplexity
+    val valid = hasCase && hasCPU && (hasRAM || !requiresRAM) && complexity <= maxComplexity
 
     val progress =
       if (!hasCPU) Localization.Assembler.InsertCPU
@@ -56,7 +58,7 @@ abstract class Template {
         warnings += Localization.Assembler.Warning(name)
       }
     }
-    if (warnings.length > 0) {
+    if (warnings.nonEmpty) {
       warnings.prepend(Localization.Assembler.Warnings)
     }
 
@@ -80,6 +82,15 @@ abstract class Template {
     case _ => false
   })
 
+  protected def requiresRAM(inventory: IInventory) = !(0 until inventory.getSizeInventory).
+    map(inventory.getStackInSlot).
+    exists(stack => api.Driver.driverFor(stack, hostClass) match {
+    case driver: Processor =>
+      val architecture = driver.architecture(stack)
+      architecture != null && architecture.getAnnotation(classOf[Architecture.NoMemoryRequirements]) != null
+    case _ => false
+  })
+
   protected def hasComponent(name: String)(inventory: IInventory) = exists(inventory, stack => Option(api.Items.get(stack)) match {
     case Some(descriptor) => descriptor.name == name
     case _ => false