@sembl/compiler

Schema compiler for SEMBL. Walks decorated TypeScript classes and emits the runtime schemas @sembl/core coerces against.

Extraction reads the source AST with ts-morph. Decorators are no-ops at runtime — nothing is reflected or evaluated — so a value that isn't written out in source can't be read, and the compiler says so rather than guessing.

See the project README for the full walkthrough.

Install

pnpm add -D @sembl/compiler

Usage

sembl extract --input src/schemas --output src/generated

Emits one <Name>.schema.ts per decorated class plus an index.ts exporting a SchemaBundle. Treat the output as a build artifact: gitignore it, and run extraction before your build.

| Flag | Notes | | ----------------- | ------------------------------------------------------------ | | -i, --input | Directory of decorated schema classes. Required. | | -o, --output | Directory for generated files. Required. | | --tsconfig | Path to a tsconfig, when type resolution needs your settings. | | --strict | Exit non-zero on warnings. Recommended in CI. |

Warnings

Warnings print to stderr and are advisory by default. They are worth reading — each one marks a place where the emitted schema is narrower or vaguer than the type you wrote:

• a @Constrain entry that isn't a compile-time literal, so it can't be read
• @ValuesFrom on a field that isn't a string or string[]
• a type with no FieldType equivalent (a Date, a Map, an index-signature object), which falls back to a string so the rest of the schema still extracts

Inline anonymous object types don't warn — they get a synthesized nested schema registered in the bundle, named after the class and property path.