improve domain class detection

One problematic scenario is when a domain class is used as a command
object, the SourceUnit that is being used to figure out if this is a
domain class or not is the source unit of the controller, not the
source unit of the domain class so the previous logic wasn’t working.

It looks like something changed that affects the order that
transformations are being run because in the scenario described above,
the domain class does not yet have the Entity annotation added to it so
it isn’t being detected as a domain class in the same way it was with
previous versions of Grails, at least in some circumstances.

Relevant functional test:
grails/grails3-functional-tests@a115c7928b4064
e6e03eb6a331f4be5d4dd800d6

fixes #10079

Author: jeffscottbrown

grails-core/src/main/groovy/org/grails/compiler/injection/GrailsASTUtils.java

@@ -726,16 +726,24 @@ public static boolean isDomainClass(final ClassNode classNode, final SourceUnit
 
         if (!isDomainClass && sourceNode != null) {
             final String sourcePath = sourceNode.getName();
-            final File sourceFile = new File(sourcePath);
-            File parent = sourceFile.getParentFile();
-            while (parent != null && !isDomainClass) {
-                final File parentParent = parent.getParentFile();
-                if (parent.getName().equals(DOMAIN_DIR) &&
-                        parentParent != null &&
-                        parentParent.getName().equals(GRAILS_APP_DIR)) {
-                    isDomainClass = true;
-                }
-                parent = parentParent;
+            final String grailsAppDirToLookFor = File.separator +
+                    GRAILS_APP_DIR + File.separator;
+            final int indexOfGrailsAppDir = sourcePath.lastIndexOf(grailsAppDirToLookFor);
+            if(indexOfGrailsAppDir >= 0) {
+                final String pathToGrailsAppDir =
+                        sourcePath.substring(0, indexOfGrailsAppDir +
+                                                grailsAppDirToLookFor.length());
+
+                final String pathToDomainDir = pathToGrailsAppDir +
+                        DOMAIN_DIR + File.separator;
+
+                final String className = classNode.getName();
+                final String relativePathToDomainSourceFile =
+                        className.replace('.', File.separatorChar) + ".groovy";
+                final String pathToDomainSourceFile = pathToDomainDir +
+                                                      relativePathToDomainSourceFile;
+
+                isDomainClass = new File(pathToDomainSourceFile).exists();
             }
         }
 

grails-core/src/test/groovy/org/grails/compiler/injection/GrailsASTUtilsSpec.groovy

@@ -0,0 +1,49 @@
+package org.grails.compiler.injection
+
+import org.codehaus.groovy.ast.ClassNode
+import org.codehaus.groovy.control.SourceUnit
+import spock.lang.Issue
+import spock.lang.Specification
+
+class GrailsASTUtilsSpec extends Specification {
+
+    @Issue('grails/grails-core#10079')
+    void 'test domain class detection when the current source unit is associated with a controller'() {
+        setup:
+        File tmpDir = new File(System.getProperty('java.io.tmpdir'))
+
+        File projectDir = new File(tmpDir, "projectDir")
+
+        // create /projectDir/grails-app/domain/ under java.io.tmpdir
+        File grailsAppDir = new File(projectDir, 'grails-app')
+        File domainDir = new File(grailsAppDir, 'domain')
+
+        String packagePath = Something.package.name.replace('.' as char, File.separatorChar)
+
+        // create the source file that would contain the source for the
+        // relevant domain class...
+        File domainPackageDir = new File(domainDir, packagePath)
+        domainPackageDir.mkdirs()
+        File domainClassFile = new File(domainPackageDir, 'Something.groovy')
+        domainClassFile.createNewFile()
+
+        // the controller source file doesn't really need to exist but we need a
+        // fully qualified path to where it would be...
+        File controllersDir = new File(grailsAppDir, 'controllers')
+        File controllerPackageDir = new File(controllersDir, packagePath)
+        File controllerClassFile = new File(controllerPackageDir,
+                                            'SomethingController.groovy')
+
+        SourceUnit controllerSourceUnit = Mock()
+        controllerSourceUnit.getName() >> controllerClassFile.absolutePath
+
+        expect: 'Something should be recognized as a domain because grails-app/domain/org/grails/compiler/injection/Something.groovy exists'
+        GrailsASTUtils.isDomainClass(new ClassNode(Something), controllerSourceUnit)
+
+        and: 'SomethingElse should NOT be recognized as a domain because grails-app/domain/org/grails/compiler/injection/SomethingElse.groovy does NOT exist'
+        !GrailsASTUtils.isDomainClass(new ClassNode(SomethingElse), controllerSourceUnit)
+    }
+}
+
+class Something {}
+class SomethingElse {}