Where is flutter.compileSdkVersion?

While building flutter app, I am getting this error.

One or more plugins require a higher Android SDK version.
Fix this issue by adding the following to C:\flutter\projects\my_app\android\app\build.gradle:
android {
  compileSdkVersion 33
  ...
}

However, in my build.gradle I have :

android {
    compileSdkVersion flutter.compileSdkVersion
...
}

But I am unable to find the location where flutter.compileSdkVersion is defined. Any idea where is this defined? I have already run flutter upgrade and flutter --version returns Flutter 3.0.5.

Newer versions of flutter

In recent versions, the setting comes from the flutter installation directory here:

<flutter-installation>/packages/flutter_tools/gradle/src/main/groovy/flutter.groovy

at the top of the file there is a class named FlutterExtension, which sets a number of static variables, e.g.

static int compileSdkVersion = 34

Older versions of flutter

To strictly answer your question, the setting comes from the flutter installation directory here:

<flutter-installation>\packages\flutter_tools\gradle\flutter.gradle

Some options to change the setting:

If you want to have the settings gathered in one place, then you could set it in the file local.properties as:

flutter.compileSdkVersion=33

And you change in your build.gradle in the following way:

android {
  compileSdkVersion localProperties.getProperty('flutter.compileSdkVersion').toInteger()
...
}

or (obviously) just set the version direct as:

android {
  compileSdkVersion 33
...
}