Compare multiple objects in Variable View

[SougandhS]

This commit provides a new feature to compare elements of commonly used objects of same types like Map, HashMap, LinkedHashMap, ConcurrentHashMap, Hashtable , IdentityHashMap, WeakHashMap, TreeMap, List, ArrayList, Stack, Vector, LinkedList, HashSet, LinkedHashSet, TreeSet, CopyOnWriteArraySet, Arrays, Wrappers and custom objects from Variables view and display differences of both either in diff view or in dialog box.

Fixes eclipse-platform/eclipse.platform#531

How to test

->Select atleast 2 objects of same type (List, Map, Set etc) from Variables view
->Choose "Compare" from menu

Result

Author checklist

• I have thoroughly tested my changes
• The change is following the coding conventions
• I have signed the Eclipse Contributor Agreement (ECA)

[SougandhS]

Hi @jukzi , could you please check this PR when you have time.

[jukzi]

have not looked at the sourcecode, only on the screenshots yet:
Sounds like a usefull feature
However It is not intuitive to understand to the user if the comparison compares equality (.equals()) or identity (==) and how it is done for nested collections/arrays (deep equals?)

[SougandhS]

have not looked at the sourcecode, only on the screenshots yet: Sounds like a usefull feature However It is not intuitive to understand to the user if the comparison compares equality (.equals()) or identity (==) and how it is done for nested collections/arrays (deep equals?)

it actually extracts contents in list,map,sets and objects and stores it as a string data then compares those data with equals()
suppose we have lists of
List l1 = new ArrayList<>(Arrays.asList("apple", "banana"));
List l2 = new ArrayList<>(Arrays.asList("apple", "banana"));
and if we do l1.equals(l2) it results true
but if we do l1.equals(l2) for list like this (having same contents but in different order) ->
List l1 = new ArrayList<>(Arrays.asList("apple", "banana"));
List l2 = new ArrayList<>(Arrays.asList("banana", "apple"));
it results false

but if we now select these objects and compare from menu we get "elements contain same data"

and it wont go nested extraction for that it simply compares with the object name and id (check reference / identity)

[jukzi]

can you use interface CharSequence instead of String implementation?

[SougandhS]

from getReferenceTypeName() and javaType() only "java.lang.String" is getting returned.

[jukzi]

All messages displayed to user (execept exceptions) should be multi language aware.

[jukzi]

It only compares exactly 2 values? Wouldn't it make sense to compare also n values?

[jukzi]

i don't get why #203 (comment) says it should be implemented in platform but this is a jdt.debug only PR

[jukzi]

it actually extracts contents in list,map,sets

I understand what it does when i look at the code but i wonder if/how that could be expressed to the user.
And what can be expected for comparing two java.util.SortedSet that have same items but different order? Are they equal? I would hope it's not only true/false but saying they have same elements but different order. And such answer could also be a valid statement of anything that does not implements Set but also for an Array for example. While a object that only implements Set without SequencedCollection can not be compared for order. However SequencedCollection is only JDK 21, so what will be the heuristic for jdk<21?

[SougandhS]

All messages displayed to user (execept exceptions) should be multi language aware.

Okay

It only compares exactly 2 values? Wouldn't it make sense to compare also n values?

As of now it compares only 2 according to the #203 , for n comparisons it will be too complex

[iloveeclipse]

If that is supposed to be implemented, it should use diff viewer support for complex types, not dialogs.

[jukzi]

for n comparisons it will be too complex

Comparing n elements is only a for-loop of comparing n-1 times 2 values each.

[SougandhS]

I understand what it does when i look at the code but i wonder if/how that could be expressed to the user. And what can be expected for comparing two java.util.SortedSet that have same items but different order? Are they equal? I would hope it's not only true/false but saying they have same elements but different order. And such answer could also be a valid statement

Yes. Totally agree. I will provide additional msgs like you suggested.

While a object that only implements Set without SequencedCollection can not be compared for order. However SequencedCollection is only JDK 21, so what will be the heuristic for jdk<21?

Actually in current implementation there is a reference check provided prior comparison, so SequencedCollection will only be able to compare other SequencedCollection

[SougandhS]

If that is supposed to be implemented, it should use diff viewer support for complex types, not dialogs.

Okay

[SougandhS]

I made few more changes and included a custom diff view for custom objects and complex objects as per @iloveeclipse suggested. now it supports n-comparisons and List,Map,Set can be campared to any of its implementations . If selected objects are only 2 then dialog box is only used if its more than 2 then diff is used. Also for Sets comparison I have eliminated its order checking to eliminate confusion.

for custom objects fields are compared with each other

for nested objects their identity/reference is checked

2 new exceptions with diff string msg

2 new exceptions with same string msg

[jukzi]

Wow, that code became really long. Unfortunatly it is hard to read when the declarations are not at the initializing code.

[SougandhS]

Wow, that code became really long. Unfortunatly it is hard to read when the declarations are not at the initializing code.

Will clean it further more

[jukzi]

Looks much better now, i don't know when i would have time to test it. maybe meanwhile some one else wants to take a look? @iloveeclipse ?

review comments applied

[jukzi]

i tested with

public class A {
	public static void main(String[] args) {	
		Set<String> s1 = java.util.concurrent.ConcurrentHashMap.newKeySet();
		s1.add("1");
		Set<String> s2 = Set.of("2");
		Set<String> s11 = Set.of("1");
		List<String> l1 = List.of("1");
		System.out.println(s1.equals(s11)); // true
		System.out.println(s1.equals(s2)); //false
		System.out.println(s1.equals(l1)); //false
	}
}

This message seems to be inconsitent:

either name both objects i.e. "s1 equals s11" or none, i.e. "Objects are equal"

For the record, the other messages shown are:

I dislike the "error" icon. its not an error when objects are of different type. its just a result of comparison:

[jukzi]

I also tried to compare 3 objects.

		Set<String> s2 = Set.of("2","3");
		Set<String> s11 = Set.of("1","3");
		Set<String> s3 = Set.of("4","3");

Results in:

looks ugly: "SL No." is unclear. dark red backgroundcolor makes a bad contrast,. The "Missing Elements" column is hard to understand. The simple Listing in the Variables View is much better to understand:

[jukzi]

For Lists:

		List<String> l1 = new ArrayList<>();
		l1.add("1");
		l1.add("3");
		List<String> l2 = List.of("3","1");

instead of "Object" better say "Collections contain same elements, but in different order" where "Collection" should be the Interface that you actually used for comparison (i did not check which Interface the implementation uses)