Description Garret Wilson 2019-11-23 17:57:19 EST

This is the oddest thing. It is so odd that I think I must be making a mistake, but I don't see how. I'm using Eclipse 2019-09 R (4.13.0) Enterprise package on Windows 10.

I have a JUnit 5 unit test. It tests parsing and reformatting an XML document, specifically the order of serialized attributes. I have a static `reformat()` method which simply does a round-trip parsing and serialization of a given string using a certain formatting profile and a couple of other parameters. It looks like this:

	@Test
	public void testAttributeOrderDefaultNamespaceDeclarationFirst() throws IOException {
		assertThat(reformat("<ordered banana=\"yellow\" foo=\"oof\" bar=\"rab\" apple=\"red\" xmlns=\"http://example/ns/\" cherry=\"red\">content</ordered>",
				BLOCK_PRE_FORMAT_PROFILE, "", ""), is("<ordered foo=\"oof\" bar=\"rab\" apple=\"red\" banana=\"yellow\" cherry=\"red\">content</ordered>"));
	}

If you look at that unit test, you'll see that it will fail because the expected string doesn't contain the `xmlns` declaration. But that's not the point of this ticket. The point of this ticket is that I can set a breakpoint on the line starting with `assertThat()` and, when the line is reached, I can do the following:

1. `F5`: steps to the next line, starting with `BLOCK_PRE_FORMAT_PROFILE`
2. `F5`: steps back to the `BLOCK_PRE_FORMAT_PROFILE` line
3. `F5`: steps to the first line of the `reformat()` method

The first two steps are a little odd, but the important thing is that step #3 steps into the `reformat()` method. So good so far.

Now let me fix the unit test by adding the `xmlns` declaration in the expected output string. I also reformat the code using my source code with my code format definition, and because the lines are longer I get this:

	@Test
	public void testAttributeOrderDefaultNamespaceDeclarationFirst() throws IOException {
		assertThat(
				reformat("<ordered banana=\"yellow\" foo=\"oof\" bar=\"rab\" apple=\"red\" xmlns=\"http://example/ns/\" cherry=\"red\">content</ordered>",
						BLOCK_PRE_FORMAT_PROFILE, "", ""),
				is("<ordered xmlns=\"http://example/ns/\" foo=\"oof\" bar=\"rab\" apple=\"red\" banana=\"yellow\" cherry=\"red\">content</ordered>"));
	}

Now the unit test passes. But again that's not the point of this ticket. Let me put a breakpoint back on the `assertThat` line, and then step through it:

1. `F5`: steps to the first line in `MatcherAssert.assertThat`:

public class MatcherAssert {
    public static <T> void assertThat(T actual, Matcher<? super T> matcher) {
        assertThat("", actual, matcher);
    }

Yes, you read that correctly: for some reason Eclipse calls the `reformat()` method but does not step into it, and passes the result directly to the matcher and I never saw what happened in between. Somehow the debugger is not stepping into the code.

It gets stranger: if I override my formatting rules and put the code back this way:

	@Test
	public void testAttributeOrderDefaultNamespaceDeclarationFirst() throws IOException {
		assertThat(reformat("<ordered banana=\"yellow\" foo=\"oof\" bar=\"rab\" apple=\"red\" xmlns=\"http://example/ns/\" cherry=\"red\">content</ordered>",
				BLOCK_PRE_FORMAT_PROFILE, "", ""), is("<ordered xmlns=\"http://example/ns/\" foo=\"oof\" bar=\"rab\" apple=\"red\" banana=\"yellow\" cherry=\"red\">content</ordered>"));
	}

The debugger now correctly steps into the code again! So it has something to do with formatting!

The even weirder thing is that when I first discovered this, not only was it not stepping into the actual code, it was actually passing a string to the matcher that had nothing at all to do with that unit test, but was actually an input string _from another test method altogether_ in the same class! I even did a full clean and rebuild within Eclipse, and the same thing happened.

This really seems to be quite a serious bug, but it sounds so outlandish that I still think maybe I'm doing something wrong. But I can't think of what I could be doing to make this behavior appear.