Add Guzzle 8 support while keeping Guzzle 7 compatible

[vencakrecl]

Fixes #621.

Allows guzzlehttp/guzzle: ^7.3 || ^8.0 and guzzlehttp/psr7: ^1.7 || ^2.0 || ^3.0, and fixes the API removals and behaviour changes Guzzle 8 introduces. Guzzle 7 stays supported; both majors are covered in CI.

What breaks under Guzzle 8

Break	Where
\GuzzleHttp\Utils::jsonEncode() removed	1007 call sites across 147 generated files
RequestException::getResponse() removed — only ResponseException subclasses carry a response	649 sync catch blocks + 649 async rejection handlers
No-response network failures are now NetworkException, not ConnectException	649 generated catch blocks
cURL errors 52, 55, 56 reclassified as NetworkException	RetryMiddlewareFactory silently stops retrying
RequestException::getHandlerContext() removed	lib/RetryMiddlewareFactory.php
Request method casing preserved verbatim	apiRequest(['method' => 'post']) sends literal post

The retry one is the quietest failure: TRANSIENT_CURL_ERROR_CODES = [52, 55, 56] are all NetworkException in Guzzle 8, so instanceof ConnectException never matches and connection-error retries become a no-op with no error. (In Guzzle 7 only 52 was ever a ConnectException, so 55 and 56 were never actually retried there either — this fixes that on both majors.)

Changes

Generated clients (codegen/, applied mechanically across 147 files)

• Request bodies use json_encode(..., JSON_THROW_ON_ERROR).
• Sync catch block and async rejection handler check for getResponse() before calling it, so a failure without a response produces an ApiException with null headers/body instead of a fatal Error. The async handler previously blew up on any responseless failure under Guzzle 7 as well.
• catch (ConnectException) becomes catch (Psr\Http\Client\NetworkExceptionInterface), which both majors implement.

Hand-written code (lib/)

• RetryMiddlewareFactory::getRetryFunctionByConnectionErrors() matches NetworkExceptionInterface and reads the cURL errno from the exception message.
• Retry deciders accept any PSR-7 RequestInterface/ResponseInterface instead of only the concrete GuzzleHttp\Psr7 classes.
• apiRequest() uppercases the method option.

Tests and CI

• New tests/Unit/GeneratedApiClientTest.php drives a generated client over a MockHandler: JSON body encoding, and error handling with and without a response, on both the sync and async paths. Verified as a real regression test by restoring an unpatched BasicApi.php — 2 errors + 1 failure, including Call to undefined method GuzzleHttp\Exception\ConnectException::getResponse().
• RetryMiddlewareFactoryTest no longer relies on the removed handler-context constructor argument.
• phpunit and phpspec now run a ['^7.3', '^8.0'] matrix.

Verification

23 tests and 139 specs pass against both guzzle 7.15.2 (with psr7 2.13.0) and guzzle 8.0.1 (with psr7 3.0.0 / promises 3.0.0). php-cs-fixer reports no changes.

Things checked and found not to be affected

• Header values: ObjectSerializer::toHeaderValue() always casts to string, so psr7 3.x's string-only header rule is satisfied.
• Psr7\Query::build(): only referenced in docblocks — ObjectSerializer::buildQuery() is a local implementation, so the new value validation does not apply.
• getConfig() in the generated API classes is the SDK's own method returning Configuration, unrelated to the removed ClientInterface::getConfig().
• Psr7\Utils::streamFor() / tryFopen() still exist in psr7 3.x and are called with strings and resources only.

Note for maintainers

codegen/ is generated outside this repository, and upstream openapi-generator's php/api.mustache still emits \GuzzleHttp\Utils::jsonEncode() and the unguarded getResponse(). The generator templates need the same three changes, or a regeneration will revert all 147 files.

🤖 Generated with Claude Code