feat: Add file:// URI support for agent prompts (#3024)

Author: rationull

crates/chat-cli/src/cli/agent/mod.rs

@@ -67,6 +67,7 @@ use crate::util::{
     self,
     MCP_SERVER_TOOL_DELIMITER,
     directories,
+    file_uri,
 };
 
 pub const DEFAULT_AGENT_NAME: &str = "q_cli_default";
@@ -88,6 +89,12 @@ pub enum AgentConfigError {
     Io(#[from] std::io::Error),
     #[error("Failed to parse legacy mcp config: {0}")]
     BadLegacyMcpConfig(#[from] eyre::Report),
+    #[error("File URI not found: {uri} (resolved to {path})")]
+    FileUriNotFound { uri: String, path: PathBuf },
+    #[error("Failed to read file URI: {uri} (resolved to {path}): {error}")]
+    FileUriReadError { uri: String, path: PathBuf, error: std::io::Error },
+    #[error("Invalid file URI format: {uri}")]
+    InvalidFileUri { uri: String },
 }
 
 /// An [Agent] is a declarative way of configuring a given instance of q chat. Currently, it is
@@ -221,10 +228,15 @@ impl Agent {
         legacy_mcp_config: Option<&McpServerConfig>,
         output: &mut impl Write,
     ) -> Result<(), AgentConfigError> {
-        let Self { mcp_servers, .. } = self;
-
         self.path = Some(path.to_path_buf());
 
+        // Resolve file:// URIs in the prompt field
+        if let Some(resolved_prompt) = self.resolve_prompt()? {
+            self.prompt = Some(resolved_prompt);
+        }
+
+        let Self { mcp_servers, .. } = self;
+
         if let (true, Some(legacy_mcp_config)) = (self.use_legacy_mcp_json, legacy_mcp_config) {
             for (name, legacy_server) in &legacy_mcp_config.mcp_servers {
                 if mcp_servers.mcp_servers.contains_key(name) {
@@ -283,6 +295,48 @@ impl Agent {
         Ok(serde_json::to_string_pretty(&agent_clone)?)
     }
 
+    /// Resolves the prompt field, handling file:// URIs if present.
+    /// Returns the prompt content as-is if it doesn't start with file://,
+    /// or resolves the file URI and returns the file content.
+    pub fn resolve_prompt(&self) -> Result<Option<String>, AgentConfigError> {
+        match &self.prompt {
+            None => Ok(None),
+            Some(prompt_str) => {
+                if prompt_str.starts_with("file://") {
+                    // Get the base path from the agent config file path
+                    let base_path = match &self.path {
+                        Some(path) => path.parent().unwrap_or(Path::new(".")),
+                        None => Path::new("."),
+                    };
+
+                    // Resolve the file URI
+                    match file_uri::resolve_file_uri(prompt_str, base_path) {
+                        Ok(content) => Ok(Some(content)),
+                        Err(file_uri::FileUriError::InvalidUri { uri }) => {
+                            Err(AgentConfigError::InvalidFileUri { uri })
+                        }
+                        Err(file_uri::FileUriError::FileNotFound { path }) => {
+                            Err(AgentConfigError::FileUriNotFound {
+                                uri: prompt_str.clone(),
+                                path
+                            })
+                        }
+                        Err(file_uri::FileUriError::ReadError { path, source }) => {
+                            Err(AgentConfigError::FileUriReadError {
+                                uri: prompt_str.clone(),
+                                path,
+                                error: source
+                            })
+                        }
+                    }
+                } else {
+                    // Return the prompt as-is for backward compatibility
+                    Ok(Some(prompt_str.clone()))
+                }
+            }
+        }
+    }
+
     /// Retrieves an agent by name. It does so via first seeking the given agent under local dir,
     /// and falling back to global dir if it does not exist in local.
     pub async fn get_agent_by_name(os: &Os, agent_name: &str) -> eyre::Result<(Agent, PathBuf)> {
@@ -937,6 +991,8 @@ fn validate_agent_name(name: &str) -> eyre::Result<()> {
 #[cfg(test)]
 mod tests {
     use serde_json::json;
+    use std::fs;
+    use tempfile::TempDir;
 
     use super::*;
     use crate::cli::agent::hook::Source;
@@ -1400,4 +1456,124 @@ mod tests {
             }
         }
     }
+
+    #[test]
+    fn test_resolve_prompt_file_uri_relative() {
+        let temp_dir = TempDir::new().unwrap();
+
+        // Create a prompt file
+        let prompt_content = "You are a test agent with specific instructions.";
+        let prompt_file = temp_dir.path().join("test-prompt.md");
+        fs::write(&prompt_file, prompt_content).unwrap();
+
+        // Create agent config file path
+        let config_file = temp_dir.path().join("test-agent.json");
+
+        // Create agent with file:// URI prompt
+        let agent = Agent {
+            name: "test-agent".to_string(),
+            prompt: Some("file://./test-prompt.md".to_string()),
+            path: Some(config_file),
+            ..Default::default()
+        };
+
+        // Test resolve_prompt
+        let resolved = agent.resolve_prompt().unwrap();
+        assert_eq!(resolved, Some(prompt_content.to_string()));
+    }
+
+    #[test]
+    fn test_resolve_prompt_file_uri_absolute() {
+        let temp_dir = TempDir::new().unwrap();
+
+        // Create a prompt file
+        let prompt_content = "Absolute path prompt content.";
+        let prompt_file = temp_dir.path().join("absolute-prompt.md");
+        fs::write(&prompt_file, prompt_content).unwrap();
+
+        // Create agent with absolute file:// URI
+        let agent = Agent {
+            name: "test-agent".to_string(),
+            prompt: Some(format!("file://{}", prompt_file.display())),
+            path: Some(temp_dir.path().join("test-agent.json")),
+            ..Default::default()
+        };
+
+        // Test resolve_prompt
+        let resolved = agent.resolve_prompt().unwrap();
+        assert_eq!(resolved, Some(prompt_content.to_string()));
+    }
+
+    #[test]
+    fn test_resolve_prompt_inline_unchanged() {
+        let temp_dir = TempDir::new().unwrap();
+
+        // Create agent with inline prompt
+        let inline_prompt = "This is an inline prompt.";
+        let agent = Agent {
+            name: "test-agent".to_string(),
+            prompt: Some(inline_prompt.to_string()),
+            path: Some(temp_dir.path().join("test-agent.json")),
+            ..Default::default()
+        };
+
+        // Test resolve_prompt
+        let resolved = agent.resolve_prompt().unwrap();
+        assert_eq!(resolved, Some(inline_prompt.to_string()));
+    }
+
+    #[test]
+    fn test_resolve_prompt_file_not_found_error() {
+        let temp_dir = TempDir::new().unwrap();
+
+        // Create agent with non-existent file URI
+        let agent = Agent {
+            name: "test-agent".to_string(),
+            prompt: Some("file://./nonexistent.md".to_string()),
+            path: Some(temp_dir.path().join("test-agent.json")),
+            ..Default::default()
+        };
+
+        // Test resolve_prompt should fail
+        let result = agent.resolve_prompt();
+        assert!(result.is_err());
+
+        if let Err(AgentConfigError::FileUriNotFound { uri, .. }) = result {
+            assert_eq!(uri, "file://./nonexistent.md");
+        } else {
+            panic!("Expected FileUriNotFound error, got: {:?}", result);
+        }
+    }
+
+    #[test]
+    fn test_resolve_prompt_no_prompt_field() {
+        let temp_dir = TempDir::new().unwrap();
+
+        // Create agent without prompt field
+        let agent = Agent {
+            name: "test-agent".to_string(),
+            prompt: None,
+            path: Some(temp_dir.path().join("test-agent.json")),
+            ..Default::default()
+        };
+
+        // Test resolve_prompt
+        let resolved = agent.resolve_prompt().unwrap();
+        assert_eq!(resolved, None);
+    }
+
+    #[test]
+    fn test_resolve_prompt_no_path_set() {
+        // Create agent without path set (should not happen in practice)
+        let agent = Agent {
+            name: "test-agent".to_string(),
+            prompt: Some("file://./test.md".to_string()),
+            path: None,
+            ..Default::default()
+        };
+
+        // Test resolve_prompt should fail gracefully
+        let result = agent.resolve_prompt();
+        assert!(result.is_err());
+    }
 }

crates/chat-cli/src/util/file_uri.rs

@@ -0,0 +1,140 @@
+use std::fs;
+use std::path::{Path, PathBuf};
+
+use eyre::Result;
+use thiserror::Error;
+
+#[derive(Debug, Error)]
+pub enum FileUriError {
+    #[error("Invalid file URI format: {uri}")]
+    InvalidUri { uri: String },
+    #[error("File not found: {path}")]
+    FileNotFound { path: PathBuf },
+    #[error("Failed to read file {path}: {source}")]
+    ReadError { path: PathBuf, source: std::io::Error },
+}
+
+/// Resolves a file:// URI to its content, supporting both relative and absolute paths.
+///
+/// # Arguments
+/// * `uri` - The file:// URI to resolve
+/// * `base_path` - Base path for resolving relative URIs (typically the agent config file directory)
+///
+/// # Returns
+/// The content of the file as a String
+pub fn resolve_file_uri(uri: &str, base_path: &Path) -> Result<String, FileUriError> {
+    // Validate URI format
+    if !uri.starts_with("file://") {
+        return Err(FileUriError::InvalidUri { uri: uri.to_string() });
+    }
+
+    // Extract the path part after "file://"
+    let path_str = uri.trim_start_matches("file://");
+
+    // Handle empty path
+    if path_str.is_empty() {
+        return Err(FileUriError::InvalidUri { uri: uri.to_string() });
+    }
+
+    // Resolve the path
+    let resolved_path = if path_str.starts_with('/') {
+        // Absolute path
+        PathBuf::from(path_str)
+    } else {
+        // Relative path - resolve relative to base_path
+        base_path.join(path_str)
+    };
+
+    // Check if file exists
+    if !resolved_path.exists() {
+        return Err(FileUriError::FileNotFound { path: resolved_path });
+    }
+
+    // Check if it's a file (not a directory)
+    if !resolved_path.is_file() {
+        return Err(FileUriError::FileNotFound { path: resolved_path });
+    }
+
+    // Read the file content
+    fs::read_to_string(&resolved_path)
+        .map_err(|source| FileUriError::ReadError {
+            path: resolved_path,
+            source
+        })
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::fs;
+    use tempfile::TempDir;
+
+    #[test]
+    fn test_invalid_uri_format() {
+        let base = Path::new("/tmp");
+
+        // Not a file:// URI
+        let result = resolve_file_uri("http://example.com", base);
+        assert!(matches!(result, Err(FileUriError::InvalidUri { .. })));
+
+        // Empty path
+        let result = resolve_file_uri("file://", base);
+        assert!(matches!(result, Err(FileUriError::InvalidUri { .. })));
+    }
+
+    #[test]
+    fn test_file_not_found() {
+        let base = Path::new("/tmp");
+
+        let result = resolve_file_uri("file:///nonexistent/file.txt", base);
+        assert!(matches!(result, Err(FileUriError::FileNotFound { .. })));
+    }
+
+    #[test]
+    fn test_absolute_path_resolution() -> Result<(), Box<dyn std::error::Error>> {
+        let temp_dir = TempDir::new()?;
+        let file_path = temp_dir.path().join("test.txt");
+        let content = "Hello, World!";
+        fs::write(&file_path, content)?;
+
+        let uri = format!("file://{}", file_path.display());
+        let base = Path::new("/some/other/path");
+
+        let result = resolve_file_uri(&uri, base)?;
+        assert_eq!(result, content);
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_relative_path_resolution() -> Result<(), Box<dyn std::error::Error>> {
+        let temp_dir = TempDir::new()?;
+        let file_path = temp_dir.path().join("subdir").join("test.txt");
+        fs::create_dir_all(file_path.parent().unwrap())?;
+        let content = "Relative content";
+        fs::write(&file_path, content)?;
+
+        let uri = "file://subdir/test.txt";
+        let base = temp_dir.path();
+
+        let result = resolve_file_uri(uri, base)?;
+        assert_eq!(result, content);
+
+        Ok(())
+    }
+
+    #[test]
+    fn test_directory_instead_of_file() -> Result<(), Box<dyn std::error::Error>> {
+        let temp_dir = TempDir::new()?;
+        let dir_path = temp_dir.path().join("testdir");
+        fs::create_dir(&dir_path)?;
+
+        let uri = format!("file://{}", dir_path.display());
+        let base = Path::new("/tmp");
+
+        let result = resolve_file_uri(&uri, base);
+        assert!(matches!(result, Err(FileUriError::FileNotFound { .. })));
+
+        Ok(())
+    }
+}

crates/chat-cli/src/util/mod.rs

@@ -1,5 +1,6 @@
 pub mod consts;
 pub mod directories;
+pub mod file_uri;
 pub mod editor;
 pub mod knowledge_store;
 pub mod open;