Add --allow-prerelease and --no-sdk-version options to dotnet new globaljson template

[Copilot]

dotnet new globaljson had no way to set allowPrerelease in the generated global.json, requiring users to manually look up the field name and add it by hand. Additionally, the template always included an SDK version, preventing users from creating a minimal global.json with only allowPrerelease set.

Template changes

• Added AllowPrerelease choice parameter ("true" / "false") to template.json with defaultValue: "" (omitted from output when unspecified — fully backward compatible) and defaultIfOptionWithoutValue: "true"
• Added NoSdkVersion bool parameter to template.json with defaultValue: "false" — when set, the SDK version is omitted from the generated global.json
• Mapped to --allow-prerelease and --no-sdk-version CLI options in dotnetcli.host.json
• Restructured template conditionals to handle JSON trailing-comma validity across all combinations of the three optional fields (rollForward, allowPrerelease, version)
• Updated all 14 localization files with English placeholder strings for both new parameters

Usage

# Suppress prerelease SDKs with a specific version
dotnet new globaljson --allow-prerelease false

# Suppress prerelease SDKs without specifying a version (primary use case)
dotnet new globaljson --allow-prerelease false --no-sdk-version

# Explicit flag without value defaults to true
dotnet new globaljson --allow-prerelease

Output for --allow-prerelease false:

{
  "sdk": {
    "allowPrerelease": false,
    "version": "9.0.100"
  }
}

Output for --allow-prerelease false --no-sdk-version:

{
  "sdk": {
    "allowPrerelease": false
  }
}

Tests

• Added 5 new AllCommonItemsCreate test cases covering --allow-prerelease false, --allow-prerelease true, combined with --sdk-version, --no-sdk-version alone, and --allow-prerelease false --no-sdk-version
• Added corresponding approval snapshot files
• Updated globaljson help text snapshot to include both new options

[Mrxx99]

Why does file generated with
dotnet new globaljson --allow-prerelease false
include the SDK version? My use case was to just specify allow prerelease false without SDK version because I wanted to be on the latest SDK that is not prerelease. I know I can just remove the SDK version after creation, but the intention for the issue #32500 (that I created) was just avoiding prereleas

[marcpopMSFT]

Hmm, I missed in the original request that you didn't even want an sdk value. The current behavior includes a default value for that. We could add a --no-sdk flag but then that would have to have error checking with --sdk-version. I'm not sure we'd want --sdk-version without a value to do that as that's most likely a typo (as I expect this to be the less common scenario). We could allow --sdk-version false and somehow make that not provide a version but that's a bit odd as version expects a version.

@baronfel any thoughts on a direction to go to have allow-prerelease with no version?

[baronfel]

A --no-sdk-version could be a bit more explicit here, and it would make the conditions a bit easier to write since we have a constrained condition language in the templates.

[marcpopMSFT]

@copilot can we add a --no-sdk-version option that won't include the SDK version as there is a scenario where a customer might want all-prerelease of false but not specify a version.

[Copilot]

@copilot can we add a --no-sdk-version option that won't include the SDK version as there is a scenario where a customer might want all-prerelease of false but not specify a version.

Added --no-sdk-version in commit f08d4fa. When specified, the SDK version is omitted from the generated global.json, enabling the primary use case:

dotnet new globaljson --allow-prerelease false --no-sdk-version

Output:

{
  "sdk": {
    "allowPrerelease": false
  }
}

The template conditional logic handles all combinations of --roll-forward, --allow-prerelease, and --no-sdk-version while maintaining valid JSON (no trailing commas).

[marcpopMSFT]

@copilot when i'm testing this, I end up with an error creating the global.json and it ends halfway through.

/workspaces/test $ dotnet new globaljson --allow-prerelease false
Template "global.json file" could not be created.
Failed to create template.
Details: Error while processing file /content/GlobalJson/global.json
Unable to cast object of type 'System.String' to type 'System.Boolean'.

[Copilot]

@copilot when i'm testing this, I end up with an error creating the global.json and it ends halfway through.

...

Fixed in commit 4d1ae57. The root cause was that the template engine's And operator uses a direct C# (bool)x cast, which fails when a bool-typed parameter value is stored as the string "false". The fix changes NoSdkVersion from datatype: "bool" to datatype: "choice" (consistent with the other optional parameters AllowPrerelease, RollForward, and TestRunner), and updates all conditions to use string equality comparisons (NoSdkVersion=="" / NoSdkVersion!="") which are safe regardless of the underlying storage type.