Create .aspire/settings.json with appHostPath during aspire new

[Copilot]

Running aspire new creates a project but no .aspire/settings.json file, causing the VS Code extension to immediately prompt for appHostPath configuration after opening the project.

Changes

Modified DotNetTemplateFactory.ApplyTemplateAsync to create .aspire/settings.json after successful template instantiation:

• Added CreateSettingsFileAsync method that:
  • Searches output directory for AppHost projects (both .csproj and single-file apphost.cs)
  • Validates AppHost projects using existing GetAppHostInformationAsync infrastructure
  • Creates .aspire/settings.json with relative path to AppHost project
  • Uses JsonSourceGenerationContext for formatted output
  • Gracefully handles failures without breaking template creation

Example

Running aspire new aspire-starter --name MyApp --output ./myapp now creates:

./myapp/
├── .aspire/
│   └── settings.json          # New: {"appHostPath": "../MyApp.AppHost/MyApp.AppHost.csproj"}
├── MyApp.AppHost/
│   └── MyApp.AppHost.csproj
├── MyApp.Web/
└── MyApp.sln

Original prompt

---

This section details on the original issue you should resolve

<issue_title>aspire new should create a .aspire/settings.json file with appHostPath set after creation</issue_title>
<issue_description>This impacts the aspire extension as it will prompt you to set appHostPath immediately after opening the project</issue_description>

<agent_instructions>When running aspire new, if there is no existing appHostPath configuration setting the .aspire/settings.json file. If the file is created as part of aspire new then make sure that it is placed in the output directory and that the appHostPath is pointing to the right location relative to the location of the settings file.

It may be necessary to extract the existing logic that generates the appHostPath based on the working directory into a helper so that the base path can be overridden.</agent_instructions>

Comments on the Issue (you are @copilot in this section)

• Fixes aspire new should create a .aspire/settings.json file with appHostPath set after creation #12523

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[github-actions]

🚀 Dogfood this PR with:

⚠️ WARNING: Do not do this without first carefully reviewing the code of this PR to satisfy yourself it is safe.

curl -fsSL https://raw.githubusercontent.com/dotnet/aspire/main/eng/scripts/get-aspire-cli-pr.sh | bash -s -- 12918

Or

• Run remotely in PowerShell:

iex "& { $(irm https://raw.githubusercontent.com/dotnet/aspire/main/eng/scripts/get-aspire-cli-pr.ps1) } 12918"

[Copilot]

Pull Request Overview

This PR enhances the aspire new command to automatically create a .aspire/settings.json file with the appHostPath configuration, preventing the VS Code extension from prompting users for this setting immediately after project creation.

Key Changes

• Added automatic .aspire/settings.json file creation after successful template instantiation
• Implemented AppHost project detection for both .csproj and single-file apphost.cs formats
• Added comprehensive test coverage for the new functionality

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 5 comments.

File	Description
src/Aspire.Cli/Templating/DotNetTemplateFactory.cs	Added CreateSettingsFileAsync method to create settings file with AppHost path, and IsValidSingleFileAppHostAsync helper to validate single-file AppHost projects
tests/Aspire.Cli.Tests/Commands/NewCommandTests.cs	Added NewCommand_CreatesSettingsJsonWithAppHostPath test to verify settings file creation with correct AppHost path

[Copilot]

Missing XML documentation for the outputPath and cancellationToken parameters. According to the coding guidelines, all parameters for public and private methods should be documented when the method has a summary tag.

[Copilot]

The catch block silently swallows all exceptions without any logging. This makes debugging difficult if settings file creation fails. Consider logging the exception at a debug or warning level to aid troubleshooting while still maintaining the non-breaking behavior.

Suggested change

	catch (Exception)
	{
	// If settings file creation fails, don't fail the entire operation
	// Just continue without creating the settings file
	catch (Exception ex)
	{
	// If settings file creation fails, don't fail the entire operation
	// Just continue without creating the settings file
	AnsiConsole.MarkupLine("[yellow][[Warning]][/] Failed to create settings file: [bold]{0}[/]. Continuing without settings file.", ex.Message);
	AnsiConsole.WriteException(ex, ExceptionFormats.ShortenEverything | ExceptionFormats.ShowLinks);

[Copilot]

Missing XML documentation for this method. According to the coding guidelines, internal APIs should have brief <summary> tags explaining what the code does.

Suggested change

	/// <summary>
	/// Checks whether the specified file is a valid Aspire single file app host.
	/// </summary>

[Copilot]

The catch block swallows all exceptions without logging. Consider logging the exception at debug level to aid troubleshooting, especially since file I/O operations can fail for various reasons (permissions, encoding issues, etc.).

Suggested change

	catch
	{
	// If we can't read the file, it's not a valid candidate
	catch (Exception ex)
	{
	// If we can't read the file, it's not a valid candidate
	AnsiConsole.MarkupLine($"[grey][[Debug]] Could not read file '{candidateFile.FullName}': {ex.Message}[/]");

[Copilot]

The code duplicates the logic from ProjectLocator.CreateSettingsFileAsync (lines 422-436) which uses configurationService.SetConfigurationAsync to create the settings file. This approach would merge with existing settings if any exist. Consider extracting this into a shared helper method or using the existing IConfigurationService.SetConfigurationAsync to maintain consistency and avoid duplication.

Suggested change

	// Write the settings file
	var jsonContent = JsonSerializer.Serialize(settings, JsonSourceGenerationContext.Default.JsonObject);
	await File.WriteAllTextAsync(settingsFilePath, jsonContent, cancellationToken);
	// Write the settings file using IConfigurationService to ensure merging and consistency
	await configurationService.SetConfigurationAsync(settingsFilePath, settings, cancellationToken);