misc: Add cached() convenience function (#1006)

Author: lauzadis

.changes/cec7bdeb-990d-4e13-895e-f8ab8762a304.json

@@ -0,0 +1,5 @@
+{
+    "id": "cec7bdeb-990d-4e13-895e-f8ab8762a304",
+    "type": "feature",
+    "description": "Add a convenience function for creating `CachedCredentialsProvider`"
+}

runtime/auth/aws-credentials/api/aws-credentials.api

@@ -7,6 +7,8 @@ public final class aws/smithy/kotlin/runtime/auth/awscredentials/CachedCredentia
 
 public final class aws/smithy/kotlin/runtime/auth/awscredentials/CachedCredentialsProviderKt {
 	public static final field DEFAULT_CREDENTIALS_REFRESH_SECONDS I
+	public static final fun cached-vLdBGDU (Laws/smithy/kotlin/runtime/auth/awscredentials/CredentialsProvider;JJLaws/smithy/kotlin/runtime/time/Clock;)Laws/smithy/kotlin/runtime/auth/awscredentials/CachedCredentialsProvider;
+	public static synthetic fun cached-vLdBGDU$default (Laws/smithy/kotlin/runtime/auth/awscredentials/CredentialsProvider;JJLaws/smithy/kotlin/runtime/time/Clock;ILjava/lang/Object;)Laws/smithy/kotlin/runtime/auth/awscredentials/CachedCredentialsProvider;
 }
 
 public abstract interface class aws/smithy/kotlin/runtime/auth/awscredentials/CloseableCredentialsProvider : aws/smithy/kotlin/runtime/auth/awscredentials/CredentialsProvider, java/io/Closeable {

runtime/auth/aws-credentials/common/src/aws/smithy/kotlin/runtime/auth/awscredentials/CachedCredentialsProvider.kt

@@ -74,3 +74,21 @@ public class CachedCredentialsProvider(
         source.closeIfCloseable()
     }
 }
+
+/**
+ * A utility function which wraps a [CredentialsProvider] in a [CachedCredentialsProvider].
+ *
+ * @param expireCredentialsAfter the default expiration time period for sourced credentials. For a given set of
+ * cached credentials, the refresh time period will be the minimum of this time and any expiration timestamp on
+ * the credentials themselves.
+ * @param refreshBufferWindow amount of time before the actual credential expiration time when credentials are
+ * considered expired. For example, if credentials are expiring in 15 minutes, and the buffer time is 10 seconds,
+ * then any requests made after 14 minutes and 50 seconds will load new credentials. Defaults to 10 seconds.
+ * @param clock the source of time for this provider
+ * @return the newly-constructed credentials provider
+ */
+public fun CredentialsProvider.cached(
+    expireCredentialsAfter: Duration = DEFAULT_CREDENTIALS_REFRESH_SECONDS.seconds,
+    refreshBufferWindow: Duration = DEFAULT_CREDENTIALS_REFRESH_BUFFER_SECONDS.seconds,
+    clock: Clock = Clock.System,
+): CachedCredentialsProvider = CachedCredentialsProvider(this, expireCredentialsAfter, refreshBufferWindow, clock)

runtime/auth/aws-credentials/common/test/aws/smithy/kotlin/runtime/auth/awscredentials/CachedCredentialsProviderTest.kt

@@ -136,4 +136,18 @@ class CachedCredentialsProviderTest {
         }
         assertEquals(1, source.callCount)
     }
+
+    @Test
+    fun testCachedConvenienceFunction() = runTest {
+        val source = TestCredentialsProvider(expiration = testExpiration)
+        val provider = source.cached(clock = testClock)
+
+        val creds = provider.resolve()
+        val expected = Credentials("AKID", "secret", expiration = testExpiration)
+        assertEquals(expected, creds)
+        assertEquals(1, source.callCount)
+
+        provider.resolve()
+        assertEquals(1, source.callCount)
+    }
 }