SOLR-18092: fix solr-test-framework for 3rd party -- ExternalPaths NPE (#4225)

Co-authored-by: David Smiley <dsmiley@apache.org>

Author: dweiss

changelog/unreleased/SOLR-18171-test-framework-external-usage-NPE.yml

@@ -0,0 +1,12 @@
+title: solr-test-framework isn't usable outside Solr, a 10.0 regression.
+type: fixed
+authors:
+  - name: Dawid Weiss
+  - name: David Smiley
+  - name: Eric Pugh
+  - name: hossman
+links:
+  - name: SOLR-18092
+    url: https://issues.apache.org/jira/browse/SOLR-18092
+
+

solr/test-framework/src/java/org/apache/solr/SolrTestCase.java

@@ -25,7 +25,6 @@
 import com.carrotsearch.randomizedtesting.rules.SystemPropertiesRestoreRule;
 import com.carrotsearch.randomizedtesting.rules.TestRuleAdapter;
 import java.lang.invoke.MethodHandles;
-import java.nio.file.Files;
 import java.nio.file.Path;
 import java.util.List;
 import java.util.Objects;
@@ -130,7 +129,7 @@ public static void beforeSolrTestCase() {
       return;
     }
     final Path extPath = ExternalPaths.DEFAULT_CONFIGSET;
-    if (Files.isReadable(extPath /* implies exists() */) && Files.isDirectory(extPath)) {
+    if (extPath != null) {
       log.info(
           "Setting '{}' system property to test-framework derived value of '{}'",
           ConfigSetService.SOLR_CONFIGSET_DEFAULT_CONFDIR,

solr/test-framework/src/java/org/apache/solr/util/ExternalPaths.java

@@ -30,38 +30,38 @@
 public class ExternalPaths {
 
   /**
-   * The main directory path for the solr source being built if it can be determined. If it can not
+   * The main directory path for the solr source being built if it can be determined. If it cannot
    * be determined -- possibly because the current context is a client code base using the test
    * framework -- then this variable will be null.
    *
    * <p>Note that all other static paths available in this class are derived from the source home,
-   * and if it is null, those paths will just be relative to 'null' and may not be meaningful.
+   * and if it is null, those paths will be null as well.
    */
-  public static final Path SOURCE_HOME = determineSourceHome();
+  public static final Path SOURCE_HOME = determineSourceHome(); // absolute
 
   /**
    * @see #SOURCE_HOME
    */
-  public static Path WEBAPP_HOME = SOURCE_HOME.resolve("webapp/web").toAbsolutePath();
+  public static Path WEBAPP_HOME = SOURCE_HOME == null ? null : SOURCE_HOME.resolve("webapp/web");
 
   /**
    * @see #SOURCE_HOME
    */
   public static Path DEFAULT_CONFIGSET =
-      SOURCE_HOME.resolve("server/solr/configsets/_default/conf").toAbsolutePath();
+      SOURCE_HOME == null ? null : SOURCE_HOME.resolve("server/solr/configsets/_default/conf");
 
   /**
    * @see #SOURCE_HOME
    */
   public static Path TECHPRODUCTS_CONFIGSET =
-      SOURCE_HOME
-          .resolve("server/solr/configsets/sample_techproducts_configs/conf")
-          .toAbsolutePath();
+      SOURCE_HOME == null
+          ? null
+          : SOURCE_HOME.resolve("server/solr/configsets/sample_techproducts_configs/conf");
 
   /**
    * @see #SOURCE_HOME
    */
-  public static Path SERVER_HOME = SOURCE_HOME.resolve("server/solr").toAbsolutePath();
+  public static Path SERVER_HOME = SOURCE_HOME == null ? null : SOURCE_HOME.resolve("server/solr");
 
   /**
    * Ugly, ugly hack to determine the example home without depending on the CWD this is needed for
@@ -83,10 +83,13 @@ static Path determineSourceHome() {
       }
 
       Path base = file.toAbsolutePath();
-      while (!Files.exists(base.resolve("solr/test-framework/build.gradle")) && null != base) {
+      while (!Files.exists(base.resolve("test-framework/build.gradle"))) {
         base = base.getParent();
+        if (base == null) {
+          return null;
+        }
       }
-      return (null == base) ? null : base.resolve("solr/").toAbsolutePath();
+      return base;
     } catch (Exception e) {
       // all bets are off
       throw new SolrException(