Fix NPE in ProfileFileSupplier.defaultSupplier (#6150)

* Fix NPE in ProfileFileSupplier.defaultSupplier

* Add changelog

* Cleanup builder validation

Author: alextwoods

.changes/next-release/bugfix-AWSSDKforJavav2-30203bb.json

@@ -0,0 +1,6 @@
+{
+    "type": "bugfix",
+    "category": "AWS SDK for Java v2",
+    "contributor": "",
+    "description": "Fix NPE in `ProfileFileSupplier.defaultSupplier` when both credentials and config files do not exist."
+}

core/profiles/src/main/java/software/amazon/awssdk/profiles/ProfileFile.java

@@ -85,6 +85,13 @@ public static Aggregator aggregator() {
         return new Aggregator();
     }
 
+    /**
+     * Create an empty profile file.
+     */
+    static ProfileFile empty() {
+        return new ProfileFile(Collections.emptyMap());
+    }
+
     /**
      * Get the default profile file, using the credentials file from "~/.aws/credentials", the config file from "~/.aws/config"
      * and the "default" profile. This default behavior can be customized using the
@@ -310,8 +317,10 @@ public void setType(Type type) {
 
         @Override
         public ProfileFile build() {
+            Validate.isTrue(content != null || contentLocation != null,
+                            "content or contentLocation must be set.");
             InputStream stream = content != null ? content :
-                                 FunctionalUtils.invokeSafely(() -> Files.newInputStream(contentLocation));
+                                  FunctionalUtils.invokeSafely(() -> Files.newInputStream(contentLocation));
 
             Validate.paramNotNull(type, "type");
             Validate.paramNotNull(stream, "content");

core/profiles/src/main/java/software/amazon/awssdk/profiles/ProfileFileSupplier.java

@@ -55,13 +55,15 @@ static ProfileFileSupplier defaultSupplier() {
             = ProfileFileLocation.configurationFileLocation()
                                  .map(path -> reloadWhenModified(path, ProfileFile.Type.CONFIGURATION));
 
-        ProfileFileSupplier supplier = () -> ProfileFile.builder().build();
+        ProfileFileSupplier supplier;
         if (credentialsSupplierOptional.isPresent() && configurationSupplierOptional.isPresent()) {
             supplier = aggregate(credentialsSupplierOptional.get(), configurationSupplierOptional.get());
         } else if (credentialsSupplierOptional.isPresent()) {
             supplier = credentialsSupplierOptional.get();
         } else if (configurationSupplierOptional.isPresent()) {
             supplier = configurationSupplierOptional.get();
+        } else {
+            supplier = fixedProfileFile(ProfileFile.empty());
         }
 
         return supplier;

core/profiles/src/test/java/software/amazon/awssdk/profiles/ProfileFileSupplierTest.java

@@ -48,6 +48,7 @@
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.api.condition.EnabledForJreRange;
 import org.junit.jupiter.api.condition.JRE;
+import software.amazon.awssdk.testutils.EnvironmentVariableHelper;
 import software.amazon.awssdk.utils.Pair;
 import software.amazon.awssdk.utils.StringInputStream;
 import software.amazon.awssdk.testutils.LogCaptor;
@@ -581,6 +582,15 @@ public void checkPermission(Permission perm) {
         }
     }
 
+    @Test
+    public void defaultSupplier_noCredentialsFiles_returnsEmptyProvider() {
+        EnvironmentVariableHelper.run(environmentVariableHelper -> {
+            environmentVariableHelper.set(ProfileFileSystemSetting.AWS_SHARED_CREDENTIALS_FILE, "no-such-file");
+            environmentVariableHelper.set(ProfileFileSystemSetting.AWS_CONFIG_FILE, "no-such-file");
+            ProfileFileSupplier supplier = ProfileFileSupplier.defaultSupplier();
+            assertThat(supplier.get().profiles()).isEmpty();
+        });
+    }
 
     private Path writeTestFile(String contents, Path path) {
         try {

core/profiles/src/test/java/software/amazon/awssdk/profiles/ProfileFileTest.java

@@ -570,6 +570,14 @@ public void returnsEmptyMap_when_AwsFilesDoNotExist() {
         assertThat(missingProfile.profiles()).isInstanceOf(Map.class);
     }
 
+    @Test
+    public void builderValidatesContentRequired() {
+        assertThatThrownBy(() -> ProfileFile.builder().type(ProfileFile.Type.CONFIGURATION).build())
+            .isInstanceOf(IllegalArgumentException.class)
+            .hasMessageContaining("content or contentLocation must be set.");
+
+    }
+
     private ProfileFile configFile(String configFile) {
         return ProfileFile.builder()
                           .content(configFile)