gnd: Prompt for new directory on collision instead of exiting with error

When the target directory already exists during `gnd init`, instead of
failing with an error, the user is now prompted to enter an alternative
directory name. This applies to all init modes: --from-contract,
--from-example, and --from-subgraph.

The new `resolve_directory_collision()` function in prompt.rs handles
the prompting loop, continuing until a non-existent directory is chosen.

Author: lutter

gnd/src/commands/init.rs

@@ -23,7 +23,7 @@ use crate::output::{step, with_spinner, Step};
 use crate::prompt::{
     get_subgraph_basename, prompt_add_another_contract, prompt_contract_address,
     prompt_contract_name, prompt_directory_with_confirm, prompt_start_block,
-    prompt_subgraph_slug_with_confirm, InitForm, SourceType,
+    prompt_subgraph_slug_with_confirm, resolve_directory_collision, InitForm, SourceType,
 };
 use crate::scaffold::{generate_scaffold, init_git, install_dependencies, ScaffoldOptions};
 use crate::services::{ContractInfo, ContractService, IpfsClient, NetworksRegistry};
@@ -325,7 +325,7 @@ async fn init_from_contract(opt: &InitOpt) -> Result<()> {
         .unwrap_or_else(|| format!("user/{}", contract_name.to_lowercase()));
 
     // Determine directory
-    let directory = opt.directory.clone().unwrap_or_else(|| {
+    let initial_directory = opt.directory.clone().unwrap_or_else(|| {
         PathBuf::from(
             subgraph_name
                 .split('/')
@@ -334,13 +334,8 @@ async fn init_from_contract(opt: &InitOpt) -> Result<()> {
         )
     });
 
-    // Check if directory already exists
-    if directory.exists() {
-        return Err(anyhow!(
-            "Directory '{}' already exists. Please choose a different name or remove the existing directory.",
-            directory.display()
-        ));
-    }
+    // Resolve directory collision by prompting for a new name if needed
+    let directory = PathBuf::from(resolve_directory_collision(&initial_directory)?);
 
     // Determine start block
     let start_block = opt
@@ -524,7 +519,7 @@ fn init_from_example(opt: &InitOpt) -> Result<()> {
     };
 
     // Determine directory - prompt if not provided and in terminal
-    let directory = if let Some(dir) = &opt.directory {
+    let initial_directory = if let Some(dir) = &opt.directory {
         dir.clone()
     } else if io::stdin().is_terminal() {
         let default_dir = get_subgraph_basename(&subgraph_name);
@@ -533,13 +528,8 @@ fn init_from_example(opt: &InitOpt) -> Result<()> {
         PathBuf::from(get_subgraph_basename(&subgraph_name))
     };
 
-    // Check if directory already exists
-    if directory.exists() {
-        return Err(anyhow!(
-            "Directory '{}' already exists. Please choose a different name or remove the existing directory.",
-            directory.display()
-        ));
-    }
+    // Resolve directory collision by prompting for a new name if needed
+    let directory = PathBuf::from(resolve_directory_collision(&initial_directory)?);
 
     // Clone example with spinner
     clone_example_with_spinner(example, &directory)?;
@@ -948,17 +938,12 @@ async fn init_from_subgraph(opt: &InitOpt) -> Result<()> {
         .unwrap_or_else(|| "composed-subgraph".to_string());
 
     // Determine directory
-    let directory = opt.directory.clone().unwrap_or_else(|| {
+    let initial_directory = opt.directory.clone().unwrap_or_else(|| {
         PathBuf::from(subgraph_name.split('/').next_back().unwrap_or("subgraph"))
     });
 
-    // Check if directory already exists
-    if directory.exists() {
-        return Err(anyhow!(
-            "Directory '{}' already exists. Please choose a different name or remove the existing directory.",
-            directory.display()
-        ));
-    }
+    // Resolve directory collision by prompting for a new name if needed
+    let directory = PathBuf::from(resolve_directory_collision(&initial_directory)?);
 
     // Generate scaffold with immutable entities
     let scaffold_options = ScaffoldOptions {

gnd/src/prompt.rs

@@ -3,6 +3,8 @@
 //! This module provides wrappers around the `inquire` crate to provide
 //! consistent prompting behavior similar to the TypeScript graph-cli.
 
+use std::path::Path;
+
 use anyhow::Result;
 use console::{style, Term};
 use inquire::validator::Validation;
@@ -321,6 +323,50 @@ pub fn prompt_directory_with_confirm(default: Option<&str>) -> Result<String> {
     Ok(dir)
 }
 
+/// Resolve directory collision by prompting for a new directory name.
+///
+/// If the given directory already exists, asks the user for an alternative
+/// directory name instead of failing with an error. Continues prompting
+/// until a non-existent directory is chosen.
+///
+/// Returns the resolved directory path as a String.
+pub fn resolve_directory_collision(initial_dir: &Path) -> Result<String> {
+    if !initial_dir.exists() {
+        return Ok(initial_dir.to_str().unwrap_or("subgraph").to_string());
+    }
+
+    // Directory exists, warn and prompt for a new name
+    eprintln!(
+        "{} Directory '{}' already exists",
+        style("!").yellow(),
+        initial_dir.display()
+    );
+
+    loop {
+        let dir = Text::new("Enter a different directory name:")
+            .with_help_message("Choose a directory that doesn't exist")
+            .with_validator(|input: &str| {
+                if input.trim().is_empty() {
+                    Ok(Validation::Invalid("Directory cannot be empty".into()))
+                } else {
+                    Ok(Validation::Valid)
+                }
+            })
+            .prompt()?;
+
+        let path = Path::new(&dir);
+        if path.exists() {
+            eprintln!(
+                "{} Directory '{}' also exists, please try another name",
+                style("!").yellow(),
+                dir
+            );
+        } else {
+            return Ok(dir);
+        }
+    }
+}
+
 /// Format a subgraph name to be valid.
 fn format_subgraph_name(name: &str) -> String {
     name.trim()