Mark properties as read-only when no write method

[remicollet]

Supported by PHP 8.1+ no change for older versions

[codecov[bot]]

Codecov Report

Merging #50 (eea6e05) into master (fbbe06a) will not change coverage. The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master      #50   +/-   ##
=======================================
  Coverage   76.82%   76.82%           
=======================================
  Files          17       17           
  Lines        3612     3612           
=======================================
  Hits         2775     2775           
  Misses        837      837           

Impacted Files	Coverage Δ
src/php_pqcancel.c	89.39% <100.00%> (ø)
src/php_pqconn.c	67.77% <100.00%> (ø)
src/php_pqcopy.c	85.98% <100.00%> (ø)
src/php_pqcur.c	69.84% <100.00%> (ø)
src/php_pqlob.c	85.92% <100.00%> (ø)
src/php_pqres.c	84.45% <100.00%> (ø)
src/php_pqstm.c	88.68% <100.00%> (ø)
src/php_pqtxn.c	54.40% <100.00%> (ø)
src/php_pqtypes.c	90.27% <100.00%> (ø)

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[m6w6]

Hmm, after a quick thought, I'm skeptical that a lot of those properties actually adhere to PHP's readonly semantics, but are rather private::set, which doesn't exist in PHP...

[m6w6]

Meaning: lots of them, may change the value during lifetime...

[remicollet]

Please check for "socket" property which use std handler, so can probably be changed...

[remicollet]

Meaning: lots of them, may change the value during lifetime...

Hmmm I understand read-only, as cannot be set by user, not as immutable...

[m6w6]

Yeah, that's what extension authors usually "declared" readonly, but if ZEND_ACC_READONLY resembles userland readonly, it means something totally different, doesn't it?

A readonly property can only be initialized once, and only from the scope where it has been declared. Any other assignment or modification of the property will result in an Error exception.

[remicollet]

Following code is very confusing

$con = new pq\Connection(PQ_DSN);
var_dump($con->status);
var_dump($con->status = 125);
var_dump($con->status);

Output:

int(0)
int(125)
int(0)

And strangely ZEND_ACC_READONLY change nothing (we may expect some error/exception)

[remicollet]

Yeah, that's what extension authors usually "declared" readonly, but if ZEND_ACC_READONLY resembles userland readonly, it means something totally different, doesn't it?

A readonly property can only be initialized once, and only from the scope where it has been declared. Any other assignment or modification of the property will result in an Error exception.

https://wiki.php.net/rfc/readonly_properties_v2 also says

However, readonly properties do not preclude interior mutability. Objects (or resources) stored in readonly properties may still be modified internally:

[remicollet]

Understood, readonly only apply to typed property, so have to

-       zend_declare_property_long(php_pqconn_class_entry, ZEND_STRL("status"), CONNECTION_BAD, ZEND_ACC_PUBLIC|ZEND_ACC_READONLY);
+       zval status_default_value;
+       ZVAL_UNDEF(&status_default_value);
+       zend_string *status_column_name = zend_string_init("status", sizeof("status") - 1, 1);
+       zend_declare_typed_property(php_pqconn_class_entry, status_column_name, &status_default_value, ZEND_ACC_PUBLIC|ZEND_ACC_READONLY, NULL, (zend_type) ZEND_TYPE_INIT_MASK(MAY_BE_LONG));

And then

Fatal error: Uncaught Error: Cannot initialize readonly property pq\Connection::$status from global scope in /work/GIT/pecl-and-ext/pq/prop.php:12

Else the readonly attribute is only for documentation (reflection)

[m6w6]

Objects (or resources) stored in readonly properties may still be modified internally

^^^^^ Read that again ;-) objects and resources (i.e. objects containing other properties, or e.g. file contents of underlying resources)

[remicollet]

OK, so we don't have same idea ;)