CHANGE @W-21310587@ - Enhance NoTrailingWhitespace rule to detect multiple consecutive empty lines

[aruntyagiTutu]

Summary

Enhanced the NoTrailingWhitespace regex rule to comprehensively detect
whitespace violations while eliminating false positives. The rule now
catches trailing whitespace after code content and multiple consecutive
empty lines, while correctly allowing single empty lines between code
sections.

What This Rule Now Catches (Violations)

1. Trailing whitespace after code content

Spaces or tabs at the end of lines that contain actual code.

Output for below code:

Example:

public void method() {    // ← violation: trailing spaces after '{'

2. Multiple consecutive empty lines

Two or more empty lines in a row anywhere in the file.

Example:
public void method1() {
    System.debug('test');
}


public void method2() {  // ← violation on the extra empty line above
    System.debug('test2');
}

3. Empty lines at end of file

Multiple newlines at EOF are caught as consecutive empty lines.

Example:
public class TestClass {
    // ... code ...
}


// ← violations on the extra empty lines above EOF

What This Rule Ignores (No Violations)

1. Single empty lines between code sections

One blank line separating methods, classes, or code blocks is allowed and
encouraged.

Example:
public void method1() {
    System.debug('test');
}

public void method2() {  // ← NO violation, single empty line is OK
    System.debug('test2');
}

2. Lines with only whitespace (when singular)

Empty lines that happen to contain spaces/tabs are treated as empty lines.
No false positives on whitespace-only lines between code sections. These are
 only flagged if they create multiple consecutive empty lines.

3. Properly formatted code

- Lines ending immediately at the last code character (no trailing
whitespace)
- Files ending with a single newline character



Technical Implementation

The regex pattern uses two alternation branches:
1. (?<=\S.*)(?<target>[ \t]+)(?=\r?\n|$) - Matches trailing spaces/tabs
after non-whitespace content
2. (?<=\r?\n\r?\n)(?<target>\r?\n) - Matches each newline appearing after
two consecutive newlines (i.e., extra empty lines)

This ensures precise violation boundaries and eliminates the false positives
 that occurred with the previous implementation where lines containing only
whitespace were incorrectly flagged.