Only schedule a build if manifest builder is enabled for project

Currently MinimalState schedules a build for every project that has any
PDE nature, this can lead to projects scanned that have no
ManifestBuilder enabled at all and creating unrelated warnings.

This now checks if the builder is enabled for the project before
scheduling a build. Also the check for possible invalid invocations is
moved up so it is triggered even if a build.properties exits.

Fix #1185

ui/org.eclipse.pde.core/src/org/eclipse/pde/internal/core/MinimalState.java

@@ -53,6 +53,7 @@
 import org.eclipse.pde.internal.build.BundleHelper;
 import org.eclipse.pde.internal.build.IPDEBuildConstants;
 import org.eclipse.pde.internal.core.builders.PDEBuilderHelper;
+import org.eclipse.pde.internal.core.natures.PDE;
 import org.eclipse.pde.internal.core.util.ManifestUtils;
 import org.eclipse.pde.internal.core.util.UtilMessages;
 import org.osgi.framework.BundleException;
@@ -300,7 +301,6 @@ public void defaultVMInstallChanged(IVMInstall previous, IVMInstall current) {
 			}
 		});
 	}
-	private static final String PDE_MANIFEST_BUILDER = "org.eclipse.pde.ManifestBuilder"; //$NON-NLS-1$
 
 	public static void triggerSystemPackagesReload() {
 		final String jobFamily = "pde.internal.ReresolveStateAfterVMorEEchanges"; //$NON-NLS-1$
@@ -336,9 +336,10 @@ public static IStatus reloadSystemPackagesIntoState() {
 		// Perform PDE-Manifest build, to re-validate all Manifests
 		MultiStatus status = new MultiStatus(MinimalState.class, 0, "Reload of JRE system-packages encountered issues"); //$NON-NLS-1$
 		for (IProject project : ResourcesPlugin.getWorkspace().getRoot().getProjects()) {
-			if (PDEBuilderHelper.isPDEProject(project)) {
+			if (PDEBuilderHelper.hasManifestBuilder(project)) {
 				try {
-					project.build(IncrementalProjectBuilder.FULL_BUILD, PDE_MANIFEST_BUILDER, null, null);
+					project.build(IncrementalProjectBuilder.FULL_BUILD, PDE.MANIFEST_BUILDER_ID, null,
+							null);
 				} catch (CoreException e) { // ignore
 					status.add(e.getStatus());
 				}

ui/org.eclipse.pde.core/src/org/eclipse/pde/internal/core/builders/ManifestConsistencyChecker.java

@@ -42,7 +42,6 @@
 import org.eclipse.pde.internal.core.PDECore;
 import org.eclipse.pde.internal.core.PDECoreMessages;
 import org.eclipse.pde.internal.core.WorkspaceModelManager;
-import org.eclipse.pde.internal.core.natures.PDE;
 import org.eclipse.pde.internal.core.project.PDEProject;
 import org.osgi.framework.Bundle;
 
@@ -247,6 +246,12 @@ private int getDeltaType(IProject project) throws CoreException {
 	}
 
 	private void validateProject(int type, IProgressMonitor monitor) {
+		if (!PDEBuilderHelper.hasManifestBuilder(getProject())) {
+			ILog.get().error(String.format(
+					"eclipse.pde/issues/1185: validateBuildPropertiesExists called for project without ManifestBuilder: %s", //$NON-NLS-1$
+					getProject().getName()), new IllegalStateException());
+			return;
+		}
 		SubMonitor subMonitor = SubMonitor.convert(monitor, PDECoreMessages.ManifestConsistencyChecker_builderTaskName, getWorkAmount(type));
 		if ((type & STRUCTURE) != 0) {
 			validateProjectStructure(type, subMonitor.split(1));
@@ -374,14 +379,6 @@ private void validateBuildPropertiesExists(IProject project) {
 			}
 			// if build.properties doesn't exist and build problems != IGNORE, create a marker on the project bug 172451
 			try {
-				if (!project.hasNature(PDE.PLUGIN_NATURE)) {
-					// how did this happen?
-					ILog.get().error(
-							"eclipse.pde/issues/1185: validateBuildPropertiesExists called for project without plugin nature: " //$NON-NLS-1$
-									+ project.getName(), 
-							new IllegalStateException());
-					return;
-				}
 				Map<String, Object> attributes = new HashMap<>();
 				attributes.put(IMarker.SEVERITY, CompilerFlags.ERROR == severity ? IMarker.SEVERITY_ERROR : IMarker.SEVERITY_WARNING);
 				attributes.put(IMarker.MESSAGE, PDECoreMessages.ManifestConsistencyChecker_buildDoesNotExist);

ui/org.eclipse.pde.core/src/org/eclipse/pde/internal/core/builders/PDEBuilderHelper.java

@@ -14,10 +14,12 @@
 package org.eclipse.pde.internal.core.builders;
 
 import java.util.ArrayList;
+import java.util.Arrays;
 import java.util.List;
 
 import org.eclipse.core.resources.IProject;
 import org.eclipse.core.resources.IResource;
+import org.eclipse.core.runtime.CoreException;
 import org.eclipse.core.runtime.IPath;
 import org.eclipse.jdt.core.IClasspathEntry;
 import org.eclipse.pde.core.build.IBuild;
@@ -76,4 +78,16 @@ public static boolean isPDEProject(IProject project) {
 				&& (PDE.hasPluginNature(project) || PDE.hasFeatureNature(project) || PDE.hasUpdateSiteNature(project));
 	}
 
+	public static boolean hasManifestBuilder(IProject project) {
+		if (project != null && project.isAccessible()) {
+			try {
+				return Arrays.stream(project.getDescription().getBuildSpec())
+						.anyMatch(cmd -> PDE.MANIFEST_BUILDER_ID.equals(cmd.getBuilderName()));
+			} catch (CoreException e) {
+				// must assume then that it has not the required builder
+			}
+		}
+		return false;
+	}
+
 }