feat: remove code for unsupported version v5 of Guzzle

.changes/nextrelease/remove-guzzlev5-support.json

@@ -0,0 +1,7 @@
+[
+  {
+    "type": "enhancement",
+    "category": "Handler",
+    "description": "Remove code for unsupported version v5 of Guzzle."
+  }
+]

CONTRIBUTING.md

@@ -117,7 +117,7 @@ we ask the same of all community contributions as well:
 ### Changelog Documents
 
 A changelog document is a small JSON blob placed in the `.changes/nextrelease`
-folder. It should be named a clearly and uniquely, akin to a branch name. It
+folder. It should be named clearly and uniquely, akin to a branch name. It
 consists of a type, category, and description as follows:
 
 ```json

phpstan.neon

@@ -6,8 +6,6 @@ parameters:
     processTimeout: 300.0
 
   excludePaths:
-      # Guzzle V5 classes & interfaces changed in V6
-      - %rootDir%/../../../src/Handler/GuzzleV5/*
       - %rootDir%/../../../src/Crypto/Polyfill/*
       - src/data/*
 
@@ -23,9 +21,6 @@ parameters:
     - '#Property Aws\\Api\\Parser\\DecodingEventStreamIterator::\$hashContext has unknown class HashContext as its type\.#'
     - '#Return typehint of method Aws\\PhpHash::getContext\(\) has invalid type HashContext\.#'
 
-    # Guzzle V5 classes & interfaces changed in V6
-    - '#Call to an undefined static method GuzzleHttp\\Client::getDefaultUserAgent\(\)\.#'
-
     # There is a check for availability of constant that phpstan does not detect. https://github.com/phpstan/phpstan/issues/2971
     - '#Access to undefined constant GuzzleHttp\\ClientInterface::MAJOR_VERSION#'
     - '#Access to undefined constant GuzzleHttp\\ClientInterface::VERSION\.#'

src/functions.php

@@ -273,18 +273,7 @@ function describe_type($input)
  */
 function default_http_handler()
 {
-    $version = guzzle_major_version();
-    // If Guzzle 6 or 7 installed
-    if ($version === 6 || $version === 7) {
-        return new \Aws\Handler\GuzzleV6\GuzzleHandler();
-    }
-
-    // If Guzzle 5 installed
-    if ($version === 5) {
-        return new \Aws\Handler\GuzzleV5\GuzzleHandler();
-    }
-
-    throw new \RuntimeException('Unknown Guzzle version: ' . $version);
+    return new \Aws\Handler\GuzzleV6\GuzzleHandler();
 }
 
 /**
@@ -294,42 +283,7 @@ function default_http_handler()
  */
 function default_user_agent()
 {
-    $version = guzzle_major_version();
-    // If Guzzle 6 or 7 installed
-    if ($version === 6 || $version === 7) {
-        return \GuzzleHttp\default_user_agent();
-    }
-
-    throw new \RuntimeException('Unknown Guzzle version: ' . $version);
-}
-
-/**
- * Get the major version of guzzle that is installed.
- *
- * @internal This function is internal and should not be used outside aws/aws-sdk-php.
- * @return int
- * @throws \RuntimeException
- */
-function guzzle_major_version()
-{
-    static $cache = null;
-    if (null !== $cache) {
-        return $cache;
-    }
-
-    if (defined('\GuzzleHttp\ClientInterface::VERSION')) {
-        $version = (string) ClientInterface::VERSION;
-        if ($version[0] === '6') {
-            return $cache = 6;
-        }
-        if ($version[0] === '5') {
-            return $cache = 5;
-        }
-    } elseif (defined('\GuzzleHttp\ClientInterface::MAJOR_VERSION')) {
-        return $cache = ClientInterface::MAJOR_VERSION;
-    }
-
-    throw new \RuntimeException('Unable to determine what Guzzle version is installed.');
+    return \GuzzleHttp\default_user_agent();
 }
 
 /**