[Fix] Tests breaking with vLLM:Main (#306)

Closes #305 

The changes in upstream that are breaking tests with vLLM:main branch
are twofolds:
1. [This PR](vllm-project/vllm#20061)
introduces[ an
import](https://github.com/vllm-project/vllm/blob/8020e98c9f033e76c97eb8261f772d59eba49c9a/vllm/model_executor/model_loader/bitsandbytes_loader.py#L23)
which is incompatible with torch 2.5.1
2. Previously, when `model_config.task` was set to `auto`, the task
could be automatically resolved in vLLM: after the post-init method of
`ModelConfig`, the `task` field was automatically replaced from `auto`
to .e.g. `generate` or `embed`). With the changes in [This
PR](vllm-project/vllm@020f58a),
the task in `model_config`, cannot be automatically resolved anymore
when it is `generate`. This doesn't look like it is intended, but rather
a side effect of adding new supported tasks. A cleaner (but longer) way
would be to do a PR to vLLM to fix that and reintroduce the automatic
resolution of `auto` task field.

This PR addresses both of the breaking changes: 
* for 1. it installs pytorch==2.7.0 in github workflows when vLLM:main
branch is used
* for 2: it infers the task through `model_config.supported_tasks`
rather than `model_config.task` now

---------

Signed-off-by: Sophie du Couédic <[email protected]>

Author: sducouedic

.github/workflows/test.yml

@@ -70,11 +70,16 @@ jobs:
             tests/**/*.py
             vllm_spyre/**/*.py
 
-      - name: "Install PyTorch"
-        if: steps.changed-src-files.outputs.any_changed == 'true'
+      - name: "Install PyTorch 2.5.1"
+        if: (steps.changed-src-files.outputs.any_changed == 'true' && !matrix.vllm_version.repo)
         run: |
           pip install torch=="2.5.1+cpu" --index-url https://download.pytorch.org/whl/cpu
 
+      - name: "Install PyTorch 2.7.0"
+        if: (steps.changed-src-files.outputs.any_changed == 'true' && matrix.vllm_version.repo)
+        run: |
+          pip install torch=="2.7.0+cpu" --index-url https://download.pytorch.org/whl/cpu
+
       - name: "Install uv"
         if: steps.changed-src-files.outputs.any_changed == 'true'
         uses: astral-sh/setup-uv@v5

vllm_spyre/platform.py

@@ -67,6 +67,9 @@ def check_and_update_config(cls, vllm_config: VllmConfig) -> None:
 
         is_decoder = model_config.task == "generate"
         is_embedding = model_config.task == "embed"
+        if model_config.task == "auto":
+            is_embedding = "embed" in model_config.supported_tasks
+            is_decoder = "generate" in model_config.supported_tasks
 
         # v0 is only supported for embedding models, and embedding models must
         # be run on v0