Editor support

tflw lsp is a real Language Server Protocol implementation — diagnostics, hover, go-to-definition, autocomplete, rename, signature help, and rich semantic highlighting, all live over debounced in-process reparsing. It speaks standard LSP over stdio, so any LSP-capable editor can use it; VS Code is the first-class client shipped today, via the tflw extension (packages/vscode in the repo).

Everything below works for both .tflw test files and tflw.config — one server, one grammar, two dialects. Every demo on this page runs the exact same resolver code the language server does, client-side — not a screenshot or a recording. The one difference is that a browser has no project on disk: the two checks that need a resolved tflw.config — unknown api <service> and unknown session names — can't run here, so they're the only errors you'll see in your editor but not in these demos.

Install

Until 1.0 the extension is a .vsix attached to a GitHub release — download it and install it with Extensions: Install from VSIX…, or:

code --install-extension tflw-vscode-0.1.0.vsix

On 1.0 day it is listed on the Visual Studio Marketplace and Open VSX, and this section becomes one ext install line. Working in the editor is the day-to-day guide.

Reload VS Code, open a .tflw file or a tflw.config, and the extension activates automatically.

Syntax highlighting + semantic coloring

Coloring comes from two layers. A static TextMate grammar handles tflw's fixed vocabulary (keywords, strings, api methods, matcher words). On top of that, the language server also serves textDocument/semanticTokens/full — it colors things the grammar structurally can't (variable/ parameter names, object-literal field keys — arbitrary user-chosen text, not fixed vocabulary) and fills in matcher/operator words and numeric literals using your editor's own semantic color palette, independent of whichever theme is active.

Below is the real classifier's output on a representative snippet, colored by category (the palette here is illustrative, not a specific VS Code theme — how rich this looks in your own editor depends on how much semantic-token coverage your theme defines; VS Code's own bundled default theme is sparser here than a fuller theme like One Dark Pro, but the extension never overrides your theme's colors, it only supplies the tokens for your theme to color):

Diagnostics + hover

Diagnostics update live as you type — the same teaching-quality errors the CLI prints (source line

• caret + "did you mean", stable TF0xx codes; see Getting started and CI, reporting & safety), surfaced as inline squiggles. Hover over one for the full message and hint without leaving the line:

Autocomplete

Context-aware completion for keywords, matcher/generator words, and in-scope variable, parameter, and action names — narrowed to what's actually valid at the cursor:

In tflw.config too, which has its own vocabulary: the top-level directives, the config keys legal in the block you're in (a defaults block is never offered an env-only key, or the other way round), and the probe … sub-clauses under an authorized target.

Go to definition

Jump from a variable, parameter, or action reference straight to where it's defined — across imported files too:

Rename

Rename a variable, parameter, or action everywhere it's used — including inside string and path interpolation holes ("{name}", /orders/{orderId}) — in one edit:

Signature help

A parameter hint while calling an action, so you don't have to jump to its definition to remember its shape:

Run from the editor

Every test is in the Test Explorer: run a file, one test, or the previous run's failures, and each verdict shows beside the test — a failure at the step that failed. The ▶ Run test and ▶ Run file lenses above every test "..." line run through the same explorer, with the same tflw binary the CLI reference covers.

Outline, references and code actions

The Outline view lists a file's tests, actions, elements and hooks; Find All References follows an action, session or element into every file that uses it; every block folds. Each reuse hint tflw check prints is a code action — Extract into action or Extract into element — that writes what tflw refactor apply writes, and a did you mean diagnostic offers its fix.

Settings

• tflw.env — which tflw.config environment diagnostics resolve services/sessions against (the same precedence slot as tflw run --env/TFLW_ENV). Leave unset to use the config's default or sole environment.