change()ing a column via a migration ignores storedAs()

[iansltx]

• Laravel Version: 8.18.2
• PHP Version: 7.4
• Database Driver & Version: MySQL 5.7 and 8.0

Description:

Specifying storedAs() (guessing virtualAs has the same problem) on a column change in a migration doesn't apply the generated column expression, silently leaving you with plain column rather than a generated one. This may be a Doctrine DBAL issue since it involves change(), but figured I'd file the issue where I experienced it.

Steps To Reproduce:

In one migration:

Schema::create('urls', function (Blueprint $table) {
    $table->bigIncrements('id');
    $table->json('response');
    $table->string('click_url')->storedAs("response->>'$.click_url'");
});

At this point you'll see the correct generated column in SHOW CREATE TABLE urls.

But once you run this:

Schema::table('urls', function (Blueprint $table) {
    $table->string('click_url', 4096)->storedAs("response->>'$.click_url'")->change();
});

You get the longer field length but lose the generated-ness.

[taylorotwell]

Changing columns is handled basically entirely by Doctrine DBAL so probably needs to be discussed there.

[maaarghk]

fyi for anyone else affected, doctrine are waiting for a PR to add support to doctrine/orm for marking fields as not updateable / not insertable so that they can stop ignoring generated fields.

in the mean time, you could quite safely work around this as so:

Schema::create('urls', function (Blueprint $table) {
    $table->bigIncrements('id');
    $table->json('response');
    $table->string('click_url')->storedAs("response->>'$.click_url'");
});

Schema::table('urls', function (Blueprint $table) {
    $table->dropColumn('click_url');
});
Schema::table('urls', function (Blueprint $table) {
    $table->string('click_url', 4096)->storedAs("response->>'$.click_url'")->after('response');
});

since the column is generated there won't be any data loss.