Fix the verbose prompt for phi. (#1097)

candle-examples/examples/phi/main.rs

@@ -59,9 +59,10 @@ impl TextGeneration {
     fn run(&mut self, prompt: &str, sample_len: usize) -> Result<()> {
         use std::io::Write;
         println!("starting the inference loop");
-        print!("{prompt}");
-        std::io::stdout().flush()?;
         let tokens = self.tokenizer.encode(prompt, true).map_err(E::msg)?;
+        if tokens.is_empty() {
+            anyhow::bail!("Empty prompts are not supported in the phi model.")
+        }
         if self.verbose_prompt {
             for (token, id) in tokens.get_tokens().iter().zip(tokens.get_ids().iter()) {
                 let token = token.replace('▁', " ").replace("<0x0A>", "\n");
@@ -74,6 +75,8 @@ impl TextGeneration {
             Some(token) => *token,
             None => anyhow::bail!("cannot find the endoftext token"),
         };
+        print!("{prompt}");
+        std::io::stdout().flush()?;
         let start_gen = std::time::Instant::now();
         for index in 0..sample_len {
             let context_size = if index > 0 { 1 } else { tokens.len() };