Improve inline breakpoint discovery when expression is multiline. Fix #521

[gayanper]

When checking for lambda expression visible in same line, instead of matching the lambda line to current source line, this fix checks if the lambda is related to the current source line as part of a expression by traversing the parents unit we find the source line.

• Fixes Breakpoint with inline lambdas work only with last one vscode-java-debug#1410
• Fixes [Critical] Cannot debug multiline nested method expression's lambda statements #521

[testforstephen]

Recursively checking the parent is not efficient, any way to return earlier?

[gayanper]

Well do you see that we could run forever where theline < sourceLine will be never reached ? Otherwise i think in most cases we will end from the first iteration where line == sourceLine right ? Only in a multiline scenario we will traverse to see if the lambda we found belongs to the same line we add a breakpoint. And I also assume this logic will be executed only for breakpoints that are installed on the source line isn't it ?

[testforstephen]

I think we could follow Eclipse’s behavior for breakpoint support on the multiline expression, which allows setting a normal line breakpoint on it directly. This is simpler than the current approach.

I found that we only need a small change on the constructor of BreakpointLocationLocator. We can use the constructor public ValidBreakpointLocationLocator(CompilationUnit compilationUnit, int lineNumber, boolean bindingsResolved, boolean bestMatch, int offset, int end) to initialize the breakpoint validator. This can recognize the multiline lambda on the selected line.

java-debug/com.microsoft.java.debug.plugin/src/main/java/com/microsoft/java/debug/plugin/internal/JdtSourceLookUpProvider.java

Lines 213 to 214 in b0c70e3

	BreakpointLocationLocator locator = new BreakpointLocationLocator(astUnit,
	sourceLine, true, true);

// passing the offset to the constructor, it can recognize the multline lambda expression well
BreakpointLocationLocator locator = new BreakpointLocationLocator(astUnit,
                        sourceLine, true, true, astUnit.getPosition(sourceLine, 0), 0);

[gayanper]

Updated the fix

[testforstephen]

LGTM, thanks for contribution.