Enhance compile time un-matched closing element

[benjamin-dreux]

One thing that is especially anoying with html is unmatched closing elements.

In a general purpose language the compiler will help with it.

In this case, I don't get why java's s type system doesn't help
I'm not even sure that we can enhance html fow to give a better feedback faster

Here is the case

public static void template (Div<?> container) {
        container
            .div()
                .h2()
                    
                .__() //h2
                .div().attrClass("row")
                    .div().attrClass("col-md-12")
                        
                        .__() //img
                    .__() //div
                .__() //div
            .__();
    }

Notice the closing element for img tag, that is missing.
Here is the error message that is produced at run time, when the templated is compiled

2024-10-05T19:11:00.145-04:00 ERROR 13800 --- [ifsr] [  restartedMain] o.s.boot.SpringApplication               : Application run failed

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'personController' defined in file [/Users/benjamindreux/Dépot/ifsr/target/classes/org/uqam/ifsr/person/PersonController.class]: Failed to instantiate [org.uqam.ifsr.person.PersonController]: Constructor threw exception
	at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:318) ~[spring-beans-6.1.13.jar:6.1.13]
	at org.springframework.beans.factory.support.ConstructorResolver.autowireConstructor(ConstructorResolver.java:306) ~[spring-beans-6.1.13.jar:6.1.13]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.autowireConstructor(AbstractAutowireCapableBeanFactory.java:1375) ~[spring-beans-6.1.13.jar:6.1.13]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBeanInstance(AbstractAutowireCapableBeanFactory.java:1212) ~[spring-beans-6.1.13.jar:6.1.13]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:562) ~[spring-beans-6.1.13.jar:6.1.13]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:522) ~[spring-beans-6.1.13.jar:6.1.13]
	at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:337) ~[spring-beans-6.1.13.jar:6.1.13]
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:234) ~[spring-beans-6.1.13.jar:6.1.13]
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:335) ~[spring-beans-6.1.13.jar:6.1.13]
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:200) ~[spring-beans-6.1.13.jar:6.1.13]
	at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:975) ~[spring-beans-6.1.13.jar:6.1.13]
	at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:971) ~[spring-context-6.1.13.jar:6.1.13]
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:625) ~[spring-context-6.1.13.jar:6.1.13]
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:146) ~[spring-boot-3.3.4.jar:3.3.4]
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:754) ~[spring-boot-3.3.4.jar:3.3.4]
	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:456) ~[spring-boot-3.3.4.jar:3.3.4]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:335) ~[spring-boot-3.3.4.jar:3.3.4]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1363) ~[spring-boot-3.3.4.jar:3.3.4]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1352) ~[spring-boot-3.3.4.jar:3.3.4]
	at org.uqam.ifsr.IfsrApplication.main(IfsrApplication.java:13) ~[classes/:na]
	at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103) ~[na:na]
	at java.base/java.lang.reflect.Method.invoke(Method.java:580) ~[na:na]
	at org.springframework.boot.devtools.restart.RestartLauncher.run(RestartLauncher.java:50) ~[spring-boot-devtools-3.3.4.jar:3.3.4]
Caused by: org.springframework.beans.BeanInstantiationException: Failed to instantiate [org.uqam.ifsr.person.PersonController]: Constructor threw exception
	at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:221) ~[spring-beans-6.1.13.jar:6.1.13]
	at org.springframework.beans.factory.support.SimpleInstantiationStrategy.instantiate(SimpleInstantiationStrategy.java:117) ~[spring-beans-6.1.13.jar:6.1.13]
	at org.springframework.beans.factory.support.ConstructorResolver.instantiate(ConstructorResolver.java:315) ~[spring-beans-6.1.13.jar:6.1.13]
	... 22 common frames omitted
Caused by: java.lang.ArrayIndexOutOfBoundsException: Index -1 out of bounds for length 1000
	at htmlflow.visitor.Indentation.tabs(Indentation.java:72) ~[htmlflow-4.0.jar:na]
	at htmlflow.visitor.HtmlVisitor.newlineAndIndent(HtmlVisitor.java:125) ~[htmlflow-4.0.jar:na]
	at htmlflow.visitor.HtmlVisitor.visitParent(HtmlVisitor.java:161) ~[htmlflow-4.0.jar:na]
	at org.xmlet.htmlapifaster.ElementVisitor.visitParentHtml(ElementVisitor.java:421) ~[htmlApiFaster-1.0.12.jar:na]
	at org.xmlet.htmlapifaster.Html.__(Html.java:29) ~[htmlApiFaster-1.0.12.jar:na]
	at org.uqam.ifsr.baseTemplate.Layout.lambda$view$1(Layout.java:45) ~[classes/:na]
	at htmlflow.HtmlFlow.preprocessing(HtmlFlow.java:52) ~[htmlflow-4.0.jar:na]
	at htmlflow.HtmlFlow.view(HtmlFlow.java:101) ~[htmlflow-4.0.jar:na]
	at org.uqam.ifsr.baseTemplate.Layout.view(Layout.java:12) ~[classes/:na]
	at org.uqam.ifsr.person.PersonController.<init>(PersonController.java:15) ~[classes/:na]
	at java.base/jdk.internal.reflect.DirectConstructorHandleAccessor.newInstance(DirectConstructorHandleAccessor.java:62) ~[na:na]
	at java.base/java.lang.reflect.Constructor.newInstanceWithCaller(Constructor.java:502) ~[na:na]
	at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:486) ~[na:na]
	at org.springframework.beans.BeanUtils.instantiateClass(BeanUtils.java:208) ~[spring-beans-6.1.13.jar:6.1.13]
	... 24 common frames omitted

If this can't be identified at compile time, then the error message should be rewritted in order to give a better context on what is happening.

Something along the line of "This is generally due to miss match in closing elements"

Hope this helps

[fmcarvalho]

It’s not possible to enforce this check at compile time.

However, we can handle this scenario at runtime by checking for negative values of indentation. If such a case occurs, we can throw a meaningful exception, for example:
IllegalStateException("Closing unmatched tag!");

Additionally, the stack trace could be made more concise by excluding intermediate calls like newLineAndIndent() and tabs(). Instead, the exception would be thrown at:

htmlflow.visitor.HtmlVisitor.visitParent(HtmlVisitor.java:161) ~[htmlflow-4.0.jar:na]
...

Nevertheless, this implementation will require a performance analysis.

[fmcarvalho]

I have tried a prototype of a PreprocessingCheckMatchingTags extending ElementVisitor, which overrides visitElement and visitParent to control matching tags. However I cannot use it as a visitor of HtmlView , which requires a HtmlVisitor rather than a ElementVisitor.
(Note that class HtmlVisitor extends ElementVisitor)

Also, I cannot extend HtmlVisitor instead, because visitElement and visitParent are final and I want to keep them like that.

For now I am not figuring out a good way of implementing this feature. My first tentative is next branch feature-check-un-matched-tags.