[JENKINS-42360] Improve validation on object method calls

Actually distinguish object method calls from generalized "expected a
symbol", and report accordingly.

pipeline-model-definition/src/main/groovy/org/jenkinsci/plugins/pipeline/modeldefinition/parser/ModelParser.groovy

@@ -882,7 +882,12 @@ class ModelParser implements Parser {
     protected String parseMethodName(MethodCallExpression exp) {
         def s = matchMethodName(exp)
         if (s==null) {
-            errorCollector.error(ModelASTValue.fromConstant(null, exp), Messages.ModelParser_ExpectedSymbol())
+            if (exp.objectExpression instanceof VariableExpression &&
+                !((VariableExpression)exp.objectExpression).isThisExpression()) {
+                errorCollector.error(ModelASTValue.fromConstant(null, exp), Messages.ModelParser_ObjectMethodCall())
+            } else {
+                errorCollector.error(ModelASTValue.fromConstant(null, exp), Messages.ModelParser_ExpectedSymbol())
+            }
             s = "error";
         }
         return s;

pipeline-model-definition/src/main/resources/org/jenkinsci/plugins/pipeline/modeldefinition/Messages.properties

@@ -62,6 +62,7 @@ ModelParser.NoArgForAgent=No argument for agent
 ModelParser.NoArgForAgentKey=No argument for agent key "{0}"
 ModelParser.NoArgForMapMethodKey=No argument for map key "{0}"
 ModelParser.NoArgForTool=No argument for tool "{0}"
+ModelParser.ObjectMethodCall=Method calls on objects not allowed outside "script" blocks.
 ModelParser.OneAgentMax=Only one agent type is allowed per agent section
 ModelParser.PipelineBlockNotAtTop={0} block must be at the top-level, not within another block.
 ModelParser.PipelineStepWithoutBlock=Expected a block with the "{0}" step

pipeline-model-definition/src/test/java/org/jenkinsci/plugins/pipeline/modeldefinition/BasicModelDefTest.java

@@ -534,7 +534,7 @@ public void libraryObjectInScript() throws Exception {
 
     @Issue("JENKINS-40657")
     @Test
-    public void libraryObjectOutsideScript() throws Exception {
+    public void libraryObjectDefinedOutsidePipeline() throws Exception {
         otherRepo.init();
         otherRepo.write("src/org/foo/Zot.groovy", "package org.foo;\n" +
                 "\n" +
@@ -553,7 +553,7 @@ public void libraryObjectOutsideScript() throws Exception {
                 new LibraryConfiguration("zot-stuff",
                         new SCMSourceRetriever(new GitSCMSource(null, otherRepo.toString(), "", "*", "", true)))));
 
-        expect("libraryObjectOutsideScript")
+        expect("libraryObjectDefinedOutsidePipeline")
                 .logContains("hello");
     }
 

pipeline-model-definition/src/test/java/org/jenkinsci/plugins/pipeline/modeldefinition/ValidatorTest.java

@@ -410,7 +410,7 @@ public void globalLibraryObjectMethodCall() throws Exception {
         // Test the case of calling a method on an object, i.e., foo.bar(1). This will fail.
         expectError("globalLibraryObjectMethodCall")
                 .logContains("MultipleCompilationErrorsException: startup failed:",
-                        Messages.ModelParser_ExpectedSymbol())
+                        Messages.ModelParser_ObjectMethodCall())
                 .go();
     }