Fix DockerComposeEnvironment duplicating image names in .env file

[Copilot]

Problem

When publishing Docker Compose environments, the .env file would contain duplicate entries for container image names if the file was regenerated. This is a regression from the change that removed the hard-coded "latest" tag for container images.

For example, after multiple publishes, the .env file could contain:

# Container image name for project1
PROJECT1_IMAGE=project1:latest

# Container image name for project1
PROJECT1_IMAGE=project1:latest

Root Cause

The issue was in the EnvFile.Add() method in src/Aspire.Hosting.Docker/EnvFile.cs. When onlyIfMissing=false is set for container image references (line 193 of DockerComposePublishingContext.cs), the method would add the key again instead of updating the existing entry.

The original logic only checked if the key existed when onlyIfMissing=true:

if (onlyIfMissing && _keys.Contains(key))
{
    return;
}
// Always adds a new line, even if key exists
_lines.Add(value is not null ? $"{key}={value}" : $"{key}=");

Solution

Modified EnvFile.Add() to implement proper upsert logic:

1. When key exists and onlyIfMissing=false: Find and update the existing line with the new value
2. When key exists and onlyIfMissing=true: Skip adding (existing behavior)
3. When key doesn't exist: Add it normally (existing behavior)

This ensures that container image names are properly updated without creating duplicate entries in the .env file.

Testing

• Added comprehensive unit tests in EnvFileTests.cs covering all scenarios
• All 56 Docker-related tests pass (50 existing + 6 new)
• Verified that existing .env file handling behavior is preserved

Fixes the issue mentioned in

aspire/src/Aspire.Hosting.Docker/DockerComposePublishingContext.cs

Lines 190 to 196 in a0eb933

	if (source is ContainerImageReference cir && cir.Resource.TryGetContainerImageName(out var imageName))
	{
	defaultValue = imageName;
	onlyIfMissing = false; // Always update the image name if it changes
	}
	envFile.Add(key, defaultValue, description, onlyIfMissing);

Original prompt

---

This section details on the original issue you should resolve

<issue_title>DockerComposeEnvironment duplicates the image name</issue_title>
<issue_description>This is a regression from the last release to fix the fact that we no longer hard code "latest". This logic needs to upsert the existing image name instead

aspire/src/Aspire.Hosting.Docker/DockerComposePublishingContext.cs

Lines 190 to 196 in a0eb933

	if (source is ContainerImageReference cir && cir.Resource.TryGetContainerImageName(out var imageName))
	{
	defaultValue = imageName;
	onlyIfMissing = false; // Always update the image name if it changes
	}
	envFile.Add(key, defaultValue, description, onlyIfMissing);

</issue_description>

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

Fixes #12309

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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 -- 12310

Or

• Run remotely in PowerShell:

iex "& { $(irm https://raw.githubusercontent.com/dotnet/aspire/main/eng/scripts/get-aspire-cli-pr.ps1) } 12310"