client: scope input-id fallback to blank-pdf only

- Restrict response input-id fallback logic to the /blank-pdf endpoint in both
sync and async file-operation paths.
- Add sync and async regression tests for /compressed-pdf confirming that missing
inputId no longer falls back to outputId and still raises validation errors for
non-blank endpoints.

Assisted-by: Codex

Author: datalogics-cgreen

src/pdfrest/client.py

@@ -1032,7 +1032,9 @@ def _post_file_operation(
             for file_id in output_ids
         ]
 
-        input_ids = raw_response.input_id or (raw_response.ids or [])
+        input_ids = raw_response.input_id
+        if not input_ids and endpoint == "/blank-pdf":
+            input_ids = raw_response.ids or []
         response_payload: dict[str, Any] = {
             "input_id": [str(file_id) for file_id in input_ids],
             "output_file": [
@@ -1308,7 +1310,9 @@ async def throttled_fetch_file_info(file_id: str) -> PdfRestFile:
                 )
             )
 
-        input_ids = raw_response.input_id or (raw_response.ids or [])
+        input_ids = raw_response.input_id
+        if not input_ids and endpoint == "/blank-pdf":
+            input_ids = raw_response.ids or []
         response_payload: dict[str, Any] = {
             "input_id": [str(file_id) for file_id in input_ids],
             "output_file": [

tests/test_compress_pdf.py

@@ -71,6 +71,42 @@ def handler(request: httpx.Request) -> httpx.Response:
     assert str(response.input_id) == str(input_file.id)
 
 
+def test_compress_pdf_requires_input_id_in_response(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    monkeypatch.delenv("PDFREST_API_KEY", raising=False)
+    input_file = make_pdf_file(PdfRestFileID.generate(1))
+    output_id = str(PdfRestFileID.generate())
+
+    seen: dict[str, int] = {"post": 0, "get": 0}
+
+    def handler(request: httpx.Request) -> httpx.Response:
+        if request.method == "POST" and request.url.path == "/compressed-pdf":
+            seen["post"] += 1
+            return httpx.Response(200, json={"outputId": [output_id]})
+        if request.method == "GET" and request.url.path == f"/resource/{output_id}":
+            seen["get"] += 1
+            return httpx.Response(
+                200,
+                json=build_file_info_payload(
+                    output_id,
+                    "compressed.pdf",
+                    "application/pdf",
+                ),
+            )
+        msg = f"Unexpected request {request.method} {request.url}"
+        raise AssertionError(msg)
+
+    transport = httpx.MockTransport(handler)
+    with (
+        PdfRestClient(api_key=VALID_API_KEY, transport=transport) as client,
+        pytest.raises(ValidationError, match="at least 1 item"),
+    ):
+        client.compress_pdf(input_file, compression_level="low")
+
+    assert seen == {"post": 1, "get": 1}
+
+
 def test_compress_pdf_custom_profile(monkeypatch: pytest.MonkeyPatch) -> None:
     monkeypatch.delenv("PDFREST_API_KEY", raising=False)
     input_file = make_pdf_file(PdfRestFileID.generate(1))
@@ -300,6 +336,41 @@ def handler(request: httpx.Request) -> httpx.Response:
     assert response.output_file.name == "async.pdf"
 
 
+@pytest.mark.asyncio
+async def test_async_compress_pdf_requires_input_id_in_response(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    monkeypatch.delenv("PDFREST_API_KEY", raising=False)
+    input_file = make_pdf_file(PdfRestFileID.generate(2))
+    output_id = str(PdfRestFileID.generate())
+
+    seen: dict[str, int] = {"post": 0, "get": 0}
+
+    def handler(request: httpx.Request) -> httpx.Response:
+        if request.method == "POST" and request.url.path == "/compressed-pdf":
+            seen["post"] += 1
+            return httpx.Response(200, json={"outputId": [output_id]})
+        if request.method == "GET" and request.url.path == f"/resource/{output_id}":
+            seen["get"] += 1
+            return httpx.Response(
+                200,
+                json=build_file_info_payload(
+                    output_id,
+                    "compressed.pdf",
+                    "application/pdf",
+                ),
+            )
+        msg = f"Unexpected request {request.method} {request.url}"
+        raise AssertionError(msg)
+
+    transport = httpx.MockTransport(handler)
+    async with AsyncPdfRestClient(api_key=ASYNC_API_KEY, transport=transport) as client:
+        with pytest.raises(ValidationError, match="at least 1 item"):
+            await client.compress_pdf(input_file, compression_level="low")
+
+    assert seen == {"post": 1, "get": 1}
+
+
 @pytest.mark.asyncio
 async def test_async_compress_pdf_custom_profile(
     monkeypatch: pytest.MonkeyPatch,