refactor(compiler): introduce TemplateSource abstraction for tsp init

[timotheeguerin]

Extracts the self-contained tsp init template-loading refactor out of #11299 into its own PR.

What

Replaces getExecutionRoot()-based template resolution in tsp init with a first-class TemplateSource abstraction, with three implementations behind one interface:

• FileSystemTemplateSource — the default (installed/node) path; reads templates/ from the compiler package root. No getExecutionRoot() dependency.
• InMemoryTemplateSource — serves the index and every template file from an in-memory map (used by the standalone single-executable to serve templates offline).
• RemoteTemplateSource — --templates-url; keeps the untrusted-source confirmation and relative-file resolution.

Why

Template loading previously went through the CompilerHost filesystem contract anchored at getExecutionRoot(), which also serves the stdlib. Serving templates from an embedded/offline source required masquerading an in-memory map as a real filesystem and overloading getExecutionRoot(). This refactor decouples template resolution from the host FS contract so each context supplies its own source, and leaves getExecutionRoot() solely for the stdlib.

Notes

• No behavior change on the normal path: init defaults to FileSystemTemplateSource.
• Language server (getTypeSpecCoreTemplates / scaffoldNewProject) and the VS Code extension keep working; the extension threads a TemplateSource through create-tsp-project.
• Backward-compatible: serverlib.ts / server/types.ts are unchanged.
• This is the first of a split of feat(standalone): bundle a pinned compiler into the single-executable #11299; the standalone single-executable feature remains in feat(standalone): bundle a pinned compiler into the single-executable #11299 and builds on top of this.

[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@typespec/compiler@11303

commit: 0249d62

[github-actions]

All changed packages have been documented.

• ✅ @typespec/compiler

Show changes

@typespec/compiler - internal ✏️

Refactor tsp init template loading around a URI-based TemplateSource abstraction. A UriTemplateSource handles local and remote templates (paths and URLs), while built-in ("core") templates are addressed through an internal: scheme that resolves to an injectable provider. This lets alternative hosts (e.g. an offline single-executable compiler) serve bundled templates via an InMemoryTemplateSource without coupling template loading to the CompilerHost filesystem.

typespec-vscode - internal ✏️

Reuse the compiler's UriTemplateSource.loadIndex() to load tsp init template indexes instead of the extension's own file/URL reading and JSON parsing, unifying how core and configured templates are loaded.

[azure-sdk-automation]

You can try these changes here

🛝 Playground	🌐 Website	🛝 VSCode Extension