Add SDK_MINOR_INT

Introduce Build.VERSION.SDK_MINOR_INT. This functions like SDK_INT, but
represents the minor version of the Android API level; SDK_INT
corresponds to the major version.

Yearly dessert releases will increment SDK_INT and set SDK_MINOR_INT to
zero. In-between desserts there may be additional, minor, releases where
SDK_INT is kept the same and SDK_MINOR_INT is incremented.

A minor release may include new APIs and resources, but must not
introduce any back compat changes. Specifically, this means that minor
releases are optional and guaranteed to not require developers to
rebuild their apps.

Bug: 350458259
Test: m
Flag: android.sdk.major_minor_versioning_scheme
Change-Id: I10d39f33ecfbd463753585224d674ceaefe83b22

2 files changed, 26 insertions, 0 deletions

diff --git a/core/api/current.txt b/core/api/current.txt
index 5e8febebee0e..9875c0276bf0 100644
--- a/core/api/current.txt
+++ b/core/api/current.txt
@@ -32771,6 +32771,7 @@ package android.os {
     field @NonNull public static final String RELEASE_OR_PREVIEW_DISPLAY;
     field @Deprecated public static final String SDK;
     field public static final int SDK_INT;
+    field @FlaggedApi("android.sdk.major_minor_versioning_scheme") public static final int SDK_MINOR_INT;
     field public static final String SECURITY_PATCH;
   }
 
diff --git a/core/java/android/os/Build.java b/core/java/android/os/Build.java
index 30d2dec8b4c4..a8267d1c9d8c 100644
--- a/core/java/android/os/Build.java
+++ b/core/java/android/os/Build.java
@@ -17,6 +17,7 @@
 package android.os;
 
 import android.Manifest;
+import android.annotation.FlaggedApi;
 import android.annotation.NonNull;
 import android.annotation.Nullable;
 import android.annotation.RequiresPermission;
@@ -28,6 +29,7 @@ import android.app.Application;
 import android.compat.annotation.UnsupportedAppUsage;
 import android.content.Context;
 import android.ravenwood.annotation.RavenwoodKeepWholeClass;
+import android.sdk.Flags;
 import android.sysprop.DeviceProperties;
 import android.sysprop.SocProperties;
 import android.sysprop.TelephonyProperties;
@@ -399,12 +401,35 @@ public class Build {
          * device. This value never changes while a device is booted, but it may
          * increase when the hardware manufacturer provides an OTA update.
          * <p>
+         * Together with {@link SDK_MINOR_INT}, this constant defines the
+         * <pre>major.minor</pre> version of Android. <pre>SDK_INT</pre> is
+         * increased and <pre>SDK_MINOR_INT</pre> is set to 0 on new Android
+         * dessert releases. Between these, Android may also release so called
+         * minor releases where <pre>SDK_INT</pre> remains unchanged and
+         * <pre>SDK_MINOR_INT</pre> is increased. Minor releases can add new
+         * APIs, and have stricter guarantees around backwards compatibility
+         * (e.g. no changes gated by <pre>targetSdkVersion</pre>) compared to
+         * major releases.
+         * <p>
          * Possible values are defined in {@link Build.VERSION_CODES}.
          */
         public static final int SDK_INT = SystemProperties.getInt(
                 "ro.build.version.sdk", 0);
 
         /**
+         * The minor SDK version of the software currently running on this hardware
+         * device. This value never changes while a device is booted, but it may
+         * increase when the hardware manufacturer provides an OTA update.
+         * <p>
+         * Together with {@link SDK_INT}, this constant defines the
+         * <pre>major.minor</pre> version of Android. See {@link SDK_INT} for
+         * more information.
+         */
+        @FlaggedApi(Flags.FLAG_MAJOR_MINOR_VERSIONING_SCHEME)
+        public static final int SDK_MINOR_INT = SystemProperties.getInt(
+                "ro.build.version.sdk_minor", 0);
+
+        /**
          * The SDK version of the software that <em>initially</em> shipped on
          * this hardware device. It <em>never</em> changes during the lifetime
          * of the device, even when {@link #SDK_INT} increases due to an OTA