devcontainer.json settings should take precedence over image metadata

[alexdima]

Testing #7248

• basically all the CLI steps in Test: Dev container image metadata #7248
• modify workspace/.devcontainer.json to be:

{
	"image": "test-base-image",
	"postAttachCommand": "echo 'Hello from the postAttachCommand in the workspace image!'",
	"customizations": {
		"vscode": {
			"extensions": ["ms-vscode.hexeditor"],
			"settings": {
				"terraform.languageServer.enable": false
			}
		}
	}
}

• (notice the above configures "terraform.languageServer.enable": false)
• Rebuild Container and open the machine settings
• observe the setting is "terraform.languageServer.enable": true instead of false.

[rzhao271]

The Terraform extension doesn't seem to install for me when I attach to the running container

[rzhao271]

@alexdima are you able to verify this issue?

[rzhao271]

I also tried rebuilding and reopening the workspace container, selecting the Alpine Linux definition. Then, I installed the Hashicorp Terraform extension, which doesn't come with the terraform.languageServer.enable setting.

[chrmarti]

Attaching to an existing container does not yet apply the metadata (like install extensions). This is tracked as #7252.

To verify:

• Reopen a folder with the following devcontainer.json in a container:

{
	"image": "mcr.microsoft.com/devcontainers/rust:1",
	"customizations": {
		"vscode": {
			"settings": {
				"rust-analyzer.checkOnSave.command": "check"
			}
		}
	}
}

• Verify in the machine settings look like:

{
	"lldb.executable": "/usr/bin/lldb",
	"files.watcherExclude": {
		"**/target/**": true
	},
	"rust-analyzer.checkOnSave.command": "check"
}

• Specifically the rust analyzer setting should be "check".