Created attachment 1050727 [details]
DroolsTemplateCommentTest.zip

Description of problem:
- This issue is related to the capabilities of Drools compiler to ignore Single line comment in Rule Template files. Imagine there is a rule template which has the following template headers defined inside it.
~~~
template header
age
type
log
~~~

- However, by mistake you write a template rule which uses a header information which is not listed above. Now, you want to comment that line so as to ensure that your Drools compiler ignores it.
~~~
template "cheesefans"

rule "Cheese fans_@{row.rowNumber}"
dialect "java" 
    when
        $person: Person(age == "@{age}")
        $cheese: Cheese(type == "@{type}")
        
        // $cheeseInvalid: Cheese(type == "@{typeFault}") 
	...	
~~~

- Now, if we try to execute this template inside "ExternalSpreadsheetCompiler.compile(..)" method it complains with the following exception.
~~~
SLF4J: Failed to load class "org.slf4j.impl.StaticLoggerBinder".
SLF4J: Defaulting to no-operation (NOP) logger implementation
SLF4J: See http://www.slf4j.org/codes.html#StaticLoggerBinder for further details.
Exception in thread "main" Exception executing consequence for rule "cheesefans" in org.drools.template.parser: java.lang.RuntimeException: [Error: unable to resolve method: java.util.HashMap.typeFault() [arglength=0]]
[Near : {... rule "Cheese fans_@{row.rowNum ....}]
             ^
[Line: 1, Column: 1]
	at org.drools.core.runtime.rule.impl.DefaultConsequenceExceptionHandler.handleException(DefaultConsequenceExceptionHandler.java:39)
	at org.drools.core.common.DefaultAgenda.fireActivation(DefaultAgenda.java:1125)
	at org.drools.core.phreak.RuleExecutor.fire(RuleExecutor.java:160)
	at org.drools.core.phreak.RuleExecutor.evaluateNetworkAndFire(RuleExecutor.java:108)
	at org.drools.core.common.DefaultAgenda.fireNextItem(DefaultAgenda.java:1016)
	at org.drools.core.common.DefaultAgenda.fireAllRules(DefaultAgenda.java:1302)
	at org.drools.core.impl.StatefulKnowledgeSessionImpl.fireAllRules(StatefulKnowledgeSessionImpl.java:1289)
	at org.drools.core.impl.StatefulKnowledgeSessionImpl.fireAllRules(StatefulKnowledgeSessionImpl.java:1262)
	at org.drools.template.parser.TemplateDataListener.finishSheet(TemplateDataListener.java:119)
	at org.drools.decisiontable.parser.xls.ExcelParser.finishSheet(ExcelParser.java:244)
	at org.drools.decisiontable.parser.xls.ExcelParser.processSheet(ExcelParser.java:186)
	at org.drools.decisiontable.parser.xls.ExcelParser.parseFile(ExcelParser.java:86)
	at org.drools.decisiontable.ExternalSpreadsheetCompiler.compile(ExternalSpreadsheetCompiler.java:140)
	at org.drools.decisiontable.ExternalSpreadsheetCompiler.compile(ExternalSpreadsheetCompiler.java:168)
	at org.drools.decisiontable.ExternalSpreadsheetCompiler.compile(ExternalSpreadsheetCompiler.java:99)
	at org.drools.decisiontable.ExternalSpreadsheetCompiler.compile(ExternalSpreadsheetCompiler.java:85)
	at org.drools.examples.templates.SimpleRuleTemplateExample.buildKBase(SimpleRuleTemplateExample.java:85)
	at org.drools.examples.templates.SimpleRuleTemplateExample.executeExample(SimpleRuleTemplateExample.java:50)
	at org.drools.examples.templates.SimpleRuleTemplateExample.main(SimpleRuleTemplateExample.java:44)
Caused by: java.lang.RuntimeException: [Error: unable to resolve method: java.util.HashMap.typeFault() [arglength=0]]
[Near : {... rule "Cheese fans_@{row.rowNum ....}]
             ^
[Line: 1, Column: 1]
	at org.drools.template.parser.DefaultGenerator.generate(DefaultGenerator.java:80)
	at org.drools.template.parser.Rule_cheesefans1206731317.defaultConsequence(Rule_cheesefans1206731317.java:7)
	at org.drools.template.parser.Rule_cheesefans1206731317DefaultConsequenceInvokerGenerated.evaluate(Unknown Source)
	at org.drools.template.parser.Rule_cheesefans1206731317DefaultConsequenceInvoker.evaluate(Unknown Source)
	at org.drools.core.common.DefaultAgenda.fireActivation(DefaultAgenda.java:1114)
	... 17 more
Caused by: [Error: unable to resolve method: java.util.HashMap.typeFault() [arglength=0]]
[Near : {... rule "Cheese fans_@{row.rowNum ....}]
             ^
[Line: 1, Column: 1]
	at org.mvel2.optimizers.impl.refl.ReflectiveAccessorOptimizer.getMethod(ReflectiveAccessorOptimizer.java:1094)
	at org.mvel2.optimizers.impl.refl.ReflectiveAccessorOptimizer.getMethod(ReflectiveAccessorOptimizer.java:1003)
	at org.mvel2.optimizers.impl.refl.ReflectiveAccessorOptimizer.getBeanProperty(ReflectiveAccessorOptimizer.java:693)
	at org.mvel2.optimizers.impl.refl.ReflectiveAccessorOptimizer.compileGetChain(ReflectiveAccessorOptimizer.java:360)
	at org.mvel2.optimizers.impl.refl.ReflectiveAccessorOptimizer.optimizeAccessor(ReflectiveAccessorOptimizer.java:163)
	at org.mvel2.ast.ASTNode.optimize(ASTNode.java:159)
	at org.mvel2.ast.ASTNode.getReducedValueAccelerated(ASTNode.java:115)
	at org.mvel2.ast.BinaryOperation.getReducedValueAccelerated(BinaryOperation.java:117)
	at org.mvel2.compiler.ExecutableAccessor.getValue(ExecutableAccessor.java:42)
	at org.mvel2.MVEL.executeExpression(MVEL.java:930)
	at org.mvel2.MVEL.executeExpression(MVEL.java:991)
	at org.mvel2.templates.res.CompiledIfNode.eval(CompiledIfNode.java:43)
	at org.mvel2.templates.res.TextNode.eval(TextNode.java:42)
	at org.mvel2.templates.res.TerminalNode.eval(TerminalNode.java:35)
	at org.mvel2.templates.res.TextNode.eval(TextNode.java:42)
	at org.mvel2.templates.res.CompiledExpressionNode.eval(CompiledExpressionNode.java:46)
	at org.mvel2.templates.res.TextNode.eval(TextNode.java:42)
	at org.mvel2.templates.res.CompiledIfNode.eval(CompiledIfNode.java:44)
	at org.mvel2.templates.res.TextNode.eval(TextNode.java:42)
	at org.mvel2.templates.res.TerminalNode.eval(TerminalNode.java:35)
	at org.mvel2.templates.res.TextNode.eval(TextNode.java:42)
	at org.mvel2.templates.res.CompiledExpressionNode.eval(CompiledExpressionNode.java:46)
	at org.mvel2.templates.res.TextNode.eval(TextNode.java:42)
	at org.mvel2.templates.res.CompiledIfNode.eval(CompiledIfNode.java:44)
	at org.mvel2.templates.res.TextNode.eval(TextNode.java:42)
	at org.mvel2.templates.res.CompiledExpressionNode.eval(CompiledExpressionNode.java:46)
	at org.mvel2.templates.res.TextNode.eval(TextNode.java:42)
	at org.mvel2.templates.res.TextNode.eval(TextNode.java:42)
	at org.mvel2.templates.TemplateRuntime.execute(TemplateRuntime.java:285)
	at org.mvel2.templates.TemplateRuntime.execute(TemplateRuntime.java:247)
	at org.mvel2.templates.TemplateRuntime.execute(TemplateRuntime.java:255)
	at org.mvel2.templates.TemplateRuntime.execute(TemplateRuntime.java:207)
	at org.drools.template.parser.DefaultGenerator.generate(DefaultGenerator.java:73)
	... 21 more

~~~

- The question is , even if I have commented that mistaken line with single line comment ("//") , why does Drools compiler throws this issue? The reason why it is an issue with the compilation as you can workaround this issue if you replace the commented line's template header with a valid one.
~~~
        // $cheeseInvalid: Cheese(type == "@{type}") 
~~~

Please investigate this issue.

Version-Release number of selected component (if applicable):
- BRMS 6.1.0
- Drools 6.2.0

How reproducible:
- Always

Steps to Reproduce:
1. Import the attached project "DroolsTemplateCommentTest.zip" in JBDS/Eclipse.
2. Run the "org.drools.examples.templates.SimpleRuleTemplateExample" class as a "Java Application" from the IDE.
3. You should see the exception as quoted above.

Actual results:
- It throws the exception quoted above.

Expected results:
- It should have run fine.

Additional info:
- Nothing