Projectfmt

Projectfmt

Use projectfmt as the formatting boundary between generated source and the destination project. Pass it the source string, intended destination path, and project boundary before writing the final file.

Integrate formatting

1. Inspect the caller's runtime and package manager.
2. Add projectfmt from npm for Node or @gadicc/projectfmt from JSR for Deno. Do not add a formatter on the destination project's behalf.
3. Identify the intended output path and the narrowest correct project root.
4. Format the generated string immediately before the caller writes it.
5. Preserve projectfmt failures and diagnostics; do not silently invoke a different formatter when the selected one is unavailable or fails.
6. Add a test using a representative destination-project fixture and its real formatter configuration.

Use the runtime-appropriate import:

// Node / npm
import { formatSource } from "projectfmt";

// Deno / JSR
import { formatSource } from "@gadicc/projectfmt";

Integrate around the eventual output path:

const rendered = renderModule(model);
const filePath = path.resolve(projectRoot, "src/generated/model.ts");

const formatted = await formatSource(rendered, {
  filePath,
  projectRoot,
});

await writeTextFile(filePath, formatted);

Keep the source in memory while formatting. The intended file does not need to exist, but its path controls configuration discovery, parser selection, ignore rules, plugins, and monorepo selection.

Choose options deliberately

• Prefer an explicit projectRoot when the caller already knows its project or workspace boundary. Discovery never searches above it.
• Use the absolute-path shorthand only when automatic root inference is the intended behavior: formatSource(source, absoluteFilePath).
• Keep the default formatter: "auto" to honor the destination project. Use an explicit formatter only when the calling feature promises that behavior.
• Set strict: true when no configured formatter or an equal-ranked ambiguity must fail. Default non-strict auto mode returns unchanged source when no formatter is configured.
• Set formatOnly: true when the operation must never apply lint fixes or assist actions. This changes Biome from configured check --write behavior to formatting only; Prettier and Deno are already format-only.
• Use formatter: "none" only for an explicit formatting opt-out.

Do not infer projectRoot from the process working directory for relative paths. Relative filePath values require an explicit projectRoot, and paths must resolve to descendant files within that boundary.

Inspect resolution and failures

Use formatSourceWithResult when the caller needs changed, ignored, or full resolution diagnostics. Use resolveFormatter to diagnose selection without formatting:

import { resolveFormatter } from "projectfmt";

const resolution = await resolveFormatter({ filePath, projectRoot });
console.log(resolution.status, resolution.formatter, resolution.reason);

Handle FormatterResolutionError for invalid options, strict-mode ambiguity, missing configuration, or unavailable selected implementations. Handle FormatterExecutionError for configuration, parsing, loading, or subprocess failures. Preserve their structured fields, stderr, and cause when wrapping them.

Availability does not change selection. Never fall through from an unavailable selected formatter to another candidate.

Respect the trust boundary

Treat destination projects as trusted code. Prettier configurations and plugins can execute JavaScript, Biome runs the project's local native binary, and Deno fmt runs the deno executable on PATH. projectRoot bounds discovery and resolution; it is not a sandbox.

Do not add network access, package installation, or temporary destination files to an integration. Ensure the destination project already provides the selected formatter implementation.

Extend only when required

Use built-in adapters for Prettier, Biome, and Deno. Add a custom FormatterAdapter only for a genuinely different formatter or project signal, and normally require an explicit projectRoot because automatic inference cannot know custom project markers.

Implement all three adapter stages: discover, probe, and format. Return absolute in-bound evidence paths, keep adapter names unique, and honor context.formatOnly. Test custom adapter validation and failure wrapping as well as successful formatting.