Enhance stack trace information for rule conflicts in BuildManager

Fixes #2278

When a builder attempts to begin or end a scheduling rule that doesn't
match the outer scope rule, the error message now includes:
- Builder name and label
- Builder class name
- Plugin ID
- Project name
- The conflicting rule

This makes it much easier to identify which builder is causing the
rule mismatch, especially in complex build scenarios with multiple
builders.

The enhancement catches IllegalArgumentException at the point where
beginRule() and endRule() are called in BuildManager.basicBuild() and
wraps it with detailed context before re-throwing.

Author: vogella

resources/bundles/org.eclipse.core.resources/src/org/eclipse/core/internal/events/BuildManager.java

@@ -288,7 +288,29 @@ private void basicBuild(int trigger, IncrementalProjectBuilder builder, Map<Stri
 				depth = getWorkManager().beginUnprotected();
 				// Acquire the rule required for running this builder
 				if (rule != null) {
-					Job.getJobManager().beginRule(rule, monitor);
+					try {
+						Job.getJobManager().beginRule(rule, monitor);
+					} catch (IllegalArgumentException e) {
+						// Enhance the error message with builder and project context
+						String builderLabel = currentBuilder.getLabel();
+						String builderClass = currentBuilder.getClass().getName();
+						String projectName = builder.getProject().getFullPath().toString();
+						String pluginId = currentBuilder.getPluginId();
+
+						String enhancedMessage = String.format(
+							"Rule conflict in builder '%s' (class: %s, plugin: %s) for project '%s'. " + //$NON-NLS-1$
+							"The builder requested rule '%s' which conflicts with the outer scope rule. " + //$NON-NLS-1$
+							"Original error: %s", //$NON-NLS-1$
+							builderLabel != null ? builderLabel : "<unknown>", //$NON-NLS-1$
+							builderClass,
+							pluginId != null ? pluginId : "<unknown>", //$NON-NLS-1$
+							projectName,
+							rule,
+							e.getMessage()
+						);
+
+						throw new IllegalArgumentException(enhancedMessage, e);
+					}
 					// Now that we've acquired the rule, changes may have been made concurrently, ensure we're pointing at the
 					// correct currentTree so delta contains concurrent changes made in areas guarded by the scheduling rule
 					if (currentTree != null) {
@@ -303,7 +325,29 @@ private void basicBuild(int trigger, IncrementalProjectBuilder builder, Map<Stri
 					getWorkManager().endUnprotected(depth);
 				}
 				if (rule != null) {
-					Job.getJobManager().endRule(rule);
+					try {
+						Job.getJobManager().endRule(rule);
+					} catch (IllegalArgumentException e) {
+						// Enhance the error message with builder and project context
+						String builderLabel = currentBuilder.getLabel();
+						String builderClass = currentBuilder.getClass().getName();
+						String projectName = builder.getProject().getFullPath().toString();
+						String pluginId = currentBuilder.getPluginId();
+
+						String enhancedMessage = String.format(
+							"Rule conflict when ending rule for builder '%s' (class: %s, plugin: %s) for project '%s'. " + //$NON-NLS-1$
+							"The builder tried to end rule '%s' which does not match the current scope. " + //$NON-NLS-1$
+							"Original error: %s", //$NON-NLS-1$
+							builderLabel != null ? builderLabel : "<unknown>", //$NON-NLS-1$
+							builderClass,
+							pluginId != null ? pluginId : "<unknown>", //$NON-NLS-1$
+							projectName,
+							rule,
+							e.getMessage()
+						);
+
+						throw new IllegalArgumentException(enhancedMessage, e);
+					}
 				}
 				// Be sure to clean up after ourselves.
 				if (clean || currentBuilder.wasForgetStateRequested()) {