fix(match): Support empty lines and comments in match expressions (closes #1956)

[claytonrcarter]

What does this do

• preserves empty lines between match arms
• collapses multiple empty lines between match arms into one empty line
• prints leading comments between match arms (Comments in match statement throw error #1956)
• prints trailing comments after match arms
  • this honors trailingCommaPHP option, though the tests for comments don't use that option, so there's no test coverage for it
• adds tests for new and changed behavior
• all changes have been formatted 😉

Current behavior on main

• all empty lines between arms are discarded
• leading and trailing comments trigger error: "Error: Comment "<comment>" was not printed. Please report this error!"

Hi, I've been using prettier/plugin-php for years, but this is my first contribution. I have no idea if I have completed all PR requirements, nor if my solution is following all of the idioms,, so please let me know and I'll glady update this.

This was a pretty easy to change once I learned how the parser and printer everything fit together. The upstream parser was already including comments in the AST for match, but the printer was not making use of them. I tried to support empty lines and comments as they are handled for function params, and I was mostly successful. The only part that I couldn't get is comments that are followed by an empty line:

• in function args, if there is an empty line between the comment and the arg, it is preserved
• in this PR, empty lines between a comment and the next match arm are discarded
• I'm not sure how important this is, though, and welcome your input!

Thank you!

Example 1: no comments

Input

match($v) {

    'a' => 1,


    'b' => 2,

    default => null
};

Output

match ($v) {
    "a" => 1,

    "b" => 2,

    default => null,
};

Current behavior on main

match ($v) {
    "a" => 1,
    "b" => 2,
    default => null,
};

Example 2: with comments

Input

match($v) {

    // first comment

    'a' => 1,


    /*
     * second comment
     */

    'b' => 2,
    default => null            // final comment
};

Output

match ($v) {
    // first comment
    "a" => 1,

    /*
     * second comment
     */
    "b" => 2,
    default => null, // final comment
};

Current behavior on main

Error: Comment "// first comment" was not printed. Please report this error!

[claytonrcarter]

Sorry for the false start. I just fixed the let/const.

[czosel]

No worries at all! I’ll try to take a closer look at this soon.

[czosel]

This looks great! Thank you for this excellent contribution 💯

[czosel]

Released in v0.19.7 🎉