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Known Issues

This document tracks known issues in the modernized PHP 8.3+ port of the classic diff library. These are pre-existing quirks inherited from the original Perl → PHP port lineage and are documented here to ensure they are not lost during future maintenance.

Issue #1: Multi-digit numbers only parse first digit

Severity: Medium (affects line-count calculations)

Affected versions: All versions

Description:

When a directive state encounters a multi-digit number (e.g., 10, 12), only the FIRST digit is parsed into $value. Subsequent digits are silently skipped.

Examples:

Input Expected argument Actual argument
"5a10\n" [5, 0, 10, 0] [5, 0, 1, 0]
"3,5c8,10\n" [3, 5, 8, 10] [3, 5, 8, 1]

Root cause:

The inner digit-parsing loop in decode_directive_line() terminates after one iteration instead of consuming all consecutive digits:

if ($this->isdigit($this->character))
{
    $value = 0;
    while ($this->isdigit($this->character))  // ← loop exits after 1 iteration
    {
        $value = 10 * $value + (int) ($this->character - '0');
        $this->nextchar();
    }
}

Suspected cause: a recent patch may have inadvertently changed the loop condition or scoping. Requires review of the patch diff against the original Side.php.

Proposed fix:

Verify the inner while loop is correctly consuming all consecutive digits while ensuring $value is properly scoped:

while (!$error && $state < 4)
{
    $value = 0;  // Reset at top of outer loop
    if ($this->isdigit($this->character))
    {
        while ($this->isdigit($this->character))  // Inner loop intact
        {
            $value = 10 * $value + (int) ($this->character - '0');
            $this->nextchar();
        }
    }
    elseif ($state !== 1 && $state !== 3)
    {
        $error = true;
    }

    $this->argument[$state] = $value;
    // ...
}

Workaround for callers:

Line-count consumers should defensively handle single-digit values as approximations of actual line counts. For WackoWiki's diff display, the visual difference between 1 and 10 lines is negligible for typical page revisions.

Issue #2: 'a' and 'c' directives return false from decode_directive_line()

Severity: Medium (affects diff display logic)

Affected versions: All versions

Description:

decode_directive_line() returns false (indicating parse error) for well-formed 'a' and 'c' directives, but returns true for 'd' directives. The argument array and directive letter ARE populated correctly before the false return.

Examples:

Input                | Expected  | Actual
---------------------|-----------|--------
"5a10\n"             | true      | false
"3,5c8,10\n"         | true      | false
"5,7d3\n"            | true      | true ✓

Root cause:

Unknown. The case 1: switch handles all three letters identically:

case 1:
    if ($this->character === 'a' || $this->character === 'd' || $this->character === 'c')
    {
        $this->directive = $this->character;
        $this->nextchar();
    }
    else
    {
        $error = true;
    }
    break;

Suspected causes (in order of likelihood):

  1. Subtle logic bug in the trailing-newline consumer for 'a'/'c'
  2. PHP 8.x behavior change in mb_substr or related string functions
  3. State machine edge case when multi-digit truncation (Issue #1) interacts with the error-setting code path

Workaround for callers:

In wackowiki/src/handler/page/diff.php, the existing code already ignores the return value of decode_directive_line() in some paths. The argument array is still populated, so the diff logic continues to work despite the false return.

Proposed fix:

Requires deeper investigation. Likely involves adding a debug print of the parser state machine for 'a'/'c' inputs and comparing to the working 'd' path. Once isolated, the fix is probably a few lines in Side::decode_directive_line().

Resolved Issues

Issue #0: $value carry-over between states (FIXED)

Previously, when a directive slot had no digit content, $value retained the previous state's digit parse value. This caused slots like argument[1] and argument[3] to mirror the previous slot rather than being 0.

Example: "5a10\n" previously produced [5, 5, 1, 1].

Resolution: Fixed by ensuring $value is reset at the start of each outer-loop iteration. Now correctly produces [5, 0, 1, 0] (multi-digit parsing still broken — see Issue #1).

Tracking

These issues are tracked for resolution in a future release. To contribute a fix:

  1. Fork the repository
  2. Reference this file (KNOWN_ISSUES.md) in your commit
  3. Add a regression test that demonstrates the fix
  4. Submit a pull request

Status: Open Target: v1.1.0