add check for real hf username

evaluate.py

@@ -10,7 +10,12 @@ from about import (
     test_repo,
     THROTTLE_MINUTES
 )
-from utils import bootstrap_metrics, clip_and_log_transform, fetch_dataset_df
+from utils import (
+    bootstrap_metrics, 
+    clip_and_log_transform, 
+    fetch_dataset_df,
+    check_page_exists,
+)
 from huggingface_hub import hf_hub_download
 import datetime
 import io
@@ -51,9 +56,25 @@ class ParticipantRecord(BaseModel):
     @field_validator("hf_username")
     @classmethod
     def validate_hf_username(cls, v: str) -> str:
+        """Validate hugging face username exists by checking the url
+
+        Parameters
+        ----------
+        username : str
+            Hugging Face username
+
+        Returns
+        -------
+        bool
+            Whether Hugging Face username is real
+        """
         v = v.strip()
         if not HF_USERNAME_RE.match(v):
             raise gr.Error("Invalid Hugging Face username (letters, numbers, -, _; min 2, max ~39).")
+    
+        hf_url = f"https://huggingface.co/{v}"
+        if not check_page_exists(hf_url, delay=2):
+            raise gr.Error("The Hugging Face username used doesn't exist. An account is required to participate.")
         return v
 
     @field_validator("display_name")

utils.py

@@ -7,6 +7,41 @@ from about import results_repo_validation, results_repo_test
 from about import METRICS, STANDARD_COLS
 from loguru import logger
 
+def check_page_exists(url: str, delay=0.2):
+    """Checks if a web page exists at the given URL.
+
+    Parameters
+    ----------
+    url : str
+        Url of the page
+    delay : float, optional
+        Seconds to wait until submitting another request, by default 0.2
+
+    Returns
+    -------
+    bool
+       If the page exists
+    """
+    import requests
+    import time
+    try:
+        response = requests.get(url, timeout=5) 
+        
+        if response.status_code == 429:
+             print(f"Warning: Rate limit hit on {url}. Waiting for 5 seconds...")
+             time.sleep(5)
+             return check_page_exists(url, delay=delay) 
+
+        return response.status_code == 200
+    
+    except requests.exceptions.RequestException as e:
+        print(f"Error checking URL {url}: {e}")
+        return False
+        
+    finally:
+        # Sleep after every request to avoid HTTPS error
+        time.sleep(delay)
+
 def make_user_clickable(name: str):
     link =f'https://huggingface.co/{name}'
     return f'<a target="_blank" href="{link}" style="color: var(--link-text-color); text-decoration: underline;text-decoration-style: dotted;">{name}</a>'