Inconsistency in PHP 8.5 deprecation of terminating case with semicolon

3 days ago by Juliette Reinders Folmer — view source — reply

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Dear Theodore and list,

I've been looking into the "Deprecate semicolon after case in switch
statement" PHP 8.5 deprecation [1] with the aim of adding a sniff for
this to the PHPCompatibility standard and I'm noticing an oddity for
which I would like to clarify whether this is intentional or an oversight.

As demonstrated in the example code provided in the deprecation RFC,
both switch case condition statements, as well as default
statements, can be ended with a semicolon.

So when I first read the RFC, I interpreted the proposal to include both
case as well as default, as, in my mind, default is just a special
case in a switch.

However, the RFC explicitly only talked about deprecating the use of a
semicolon after a case statement and the implementation has followed
this to the letter. [2]

The net result of this, is that you can now have a switch statement
with semicolons terminating case statements and default statements,
where the former (case) will result in a deprecation notice, while the
latter (default) will not. For an example, see [3]

This feels inconsistent to me and counter to the intention of the RFC,
which is stated to be:

Case statements followed by a semicolon can cause confusion, as a
developer may think they behave differently in some way from regular
case statements (e.g. preventing fallthrough), when they do not.

Which leaves me wondering what the reason was not to also deprecate
the use of a semicolon to terminate a default statement in a switch ?
I can't find any discussion about this in the original mailing list
thread [4].

Anyone would care to clarify ?

Smile,
Juliette

1:
https://wiki.php.net/rfc/deprecations_php_8_5#deprecate_semicolon_after_case_in_switch_statement
2:
https://github.com/php/php-src/commit/5f8d648af6ef4e29a3c7f2b2029d08466c12bc6f
3: https://3v4l.org/liFIK/rfc#vgit.master
4: https://externals.io/message/126000

2 days ago by Theodore Brown — view source — reply

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Dear Theodore and list,

I've been looking into the "Deprecate semicolon after case in switch statement" PHP 8.5 deprecation 1
with the aim of adding a sniff for this to the PHPCompatibility standard and I'm noticing an oddity for
which I would like to clarify whether this is intentional or an oversight.

As demonstrated in the example code provided in the deprecation RFC, both switch case condition
statements, as well as default statements, can be ended with a semicolon.

So when I first read the RFC, I interpreted the proposal to include both case as well as default,
as, in my mind, default is just a special case in a switch.

However, the RFC explicitly only talked about deprecating the use of a semicolon after a
case statement and the implementation has followed this to the letter. 2

The net result of this, is that you can now have a switch statement with semicolons
terminating case statements and default statements, where the former (case) will
result in a deprecation notice, while the latter (default) will not. For an example, see 3

This feels inconsistent to me and counter to the intention of the RFC, which is stated to be:

Case statements followed by a semicolon can cause confusion, as a developer may think they
behave differently in some way from regular case statements (e.g. preventing fallthrough),
when they do not.

Which leaves me wondering what the reason was not to also deprecate the use of a semicolon
to terminate a default statement in a switch ? I can't find any discussion about this in the
original mailing list thread 4.

Anyone would care to clarify ?

Hi Juliette,

Thank you for pointing out the discrepancy. You are correct that default is just a special
case statement, and the intention in the RFC was to output the deprecation message for default cases
as well (the example in the RFC included a default case followed by a semicolon to highlight this).

The fact that a deprecation message isn't shown for default cases is an oversight on my part
when I implemented the RFC. The merged implementation correctly updated the AST for default
case statements followed by a semicolon to support the deprecation message, but I failed to
notice that when the compiler code loops over switch cases, there is a continue statement
when handling the default case which prevents reaching the code for the deprecation.

I opened a follow-up pull request to fix this, which can hopefully be merged before
PHP 8.5 is released: https://github.com/php/php-src/pull/20172

Kind regards,
Theodore

Smile,
Juliette

2 days ago by Juliette Reinders Folmer — view source — reply

unread

Dear Theodore and list,

I've been looking into the "Deprecate semicolon after case in switch statement" PHP 8.5 deprecation [1]
with the aim of adding a sniff for this to the PHPCompatibility standard and I'm noticing an oddity for
which I would like to clarify whether this is intentional or an oversight.

As demonstrated in the example code provided in the deprecation RFC, both switch case condition
statements, as well as default statements, can be ended with a semicolon.

So when I first read the RFC, I interpreted the proposal to include both case as well as default,
as, in my mind, default is just a special case in a switch.

However, the RFC explicitly only talked about deprecating the use of a semicolon after a
case statement and the implementation has followed this to the letter. [2]

The net result of this, is that you can now have a switch statement with semicolons
terminating case statements and default statements, where the former (case) will
result in a deprecation notice, while the latter (default) will not. For an example, see [3]

This feels inconsistent to me and counter to the intention of the RFC, which is stated to be:

Case statements followed by a semicolon can cause confusion, as a developer may think they
behave differently in some way from regular case statements (e.g. preventing fallthrough),
when they do not.
Which leaves me wondering what the reason was not to also deprecate the use of a semicolon
to terminate a default statement in a switch ? I can't find any discussion about this in the
original mailing list thread [4].

Anyone would care to clarify ?
Hi Juliette,

Thank you for pointing out the discrepancy. You are correct that default is just a special
case statement, and the intention in the RFC was to output the deprecation message for default cases
as well (the example in the RFC included a default case followed by a semicolon to highlight this).

The fact that a deprecation message isn't shown for default cases is an oversight on my part
when I implemented the RFC. The merged implementation correctly updated the AST for default
case statements followed by a semicolon to support the deprecation message, but I failed to
notice that when the compiler code loops over switch cases, there is a continue statement
when handling the default case which prevents reaching the code for the deprecation.

I opened a follow-up pull request to fix this, which can hopefully be merged before
PHP 8.5 is released: https://github.com/php/php-src/pull/20172

Hi Theodore,

Ah! That explains it. Bugs happen to the best of us. Glad to hear I
didn't misunderstand the intention of the RFC.

Thanks for clarifying and for the new PR to update the deprecation
implementation. Here's me hoping it will be merged soon.

Smile,
Juliette