Add a mustache based generator and java template (PR port)

.github/workflows/sdk-tests.yml

@@ -150,3 +150,31 @@ jobs:
             git diff examples/python/generated
             exit 1
           fi
+
+  test-mustache-java-r4-example:
+    runs-on: ubuntu-latest
+
+    strategy:
+      matrix:
+        bun-version: [latest]
+        java-version: [21, 25]
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Setup Bun
+        uses: oven-sh/setup-bun@v2
+        with:
+          bun-version: ${{ matrix.bun-version }}
+
+      - name: Setup Java
+        uses: actions/setup-java@v4
+        with:
+          java-version: ${{ matrix.java-version }}
+          distribution: "temurin"
+
+      - name: Install dependencies
+        run: bun install --frozen-lockfile
+
+      - name: Run tests
+        run: make test-mustache-java-r4-example

.gitignore

@@ -49,5 +49,8 @@ examples/csharp/obj
 examples/typescript-ccda/fhir-types
 examples/typescript-ccda/tree.yaml
 examples/typescript-ccda/type-schemas
+
 examples/typescript-sql-on-fhir/fhir-types
 examples/typescript-sql-on-fhir/tree.yaml
+
+examples/mustache/mustache-java-r4-output

Makefile

@@ -61,6 +61,10 @@ test-typescript-ccda-example: typecheck format lint
 	bun run examples/typescript-ccda/generate.ts
 	$(TYPECHECK) --project examples/typescript-ccda/tsconfig.json
 
+test-mustache-java-r4-example: typecheck format lint
+	bun run examples/mustache/mustache-java-r4-gen.ts
+	$(TYPECHECK) --project examples/mustache/tsconfig.examples-mustache.json
+
 test-csharp-sdk: typecheck format prepare-aidbox-runme lint
 	$(TYPECHECK) --project examples/csharp/tsconfig.json
 	bun run examples/csharp/generate.ts

README.md

@@ -22,6 +22,7 @@
         - [Field-Level Tree Shaking](#field-level-tree-shaking)
     - [Generation](#generation)
       - [1. Writer-Based Generation (Programmatic)](#1-writer-based-generation-programmatic)
+      - [2. Mustache Template-Based Generation (Declarative)](#2-mustache-template-based-generation-declarative)
   - [Roadmap](#roadmap)
   - [Support](#support)
 - [Footnotes](#footnotes)
@@ -33,6 +34,7 @@ A powerful, extensible code generation toolkit for FHIR ([Fast Healthcare Intero
 Guides:
 
 - **[Writer Generator Guide](docs/guides/writer-generator.md)** - Build custom code generators with the Writer base class
+- **[Mustache Generator Guide](docs/guides/mustache-generator.md)** - Template-based code generation for any language
 - **[TypeSchemaIndex Guide](docs/guides/typeschema-index.md)** - Type Schema structure and utilities
 - **[Testing Generators Guide](docs/guides/testing-generators.md)** - Unit tests, snapshot testing, and best practices
 - **[Contributing Guide](CONTRIBUTING.md)** - Development setup and workflow
@@ -98,6 +100,7 @@ See the [examples/](examples/) directory for working demonstrations:
 - **[typescript-sql-on-fhir/](examples/typescript-sql-on-fhir/)** - SQL on FHIR ViewDefinition with tree shaking
 - **[python/](examples/python/)** - Python/Pydantic model generation with configurable field formats
 - **[csharp/](examples/csharp/)** - C# class generation with namespace configuration
+- **[mustache/](examples/mustache/)** - Java generation with Mustache templates and post-generation hooks
 - **[local-package-folder/](examples/local-package-folder/)** - Loading unpublished local FHIR packages
 
 For detailed documentation, see [examples/README.md](examples/README.md).
@@ -247,6 +250,20 @@ Each language writer maintains full control over output formatting while leverag
 
 **When to use**: Full control needed, complex generation logic, performance-critical, language has a dedicated writer, production-grade output
 
+#### 2. Mustache Template-Based Generation (Declarative)
+
+For custom languages or formats, use Mustache templates to define code generation rules without programming:
+
+- **Template Files**: Declarative Mustache templates that describe output structure
+- **Configuration**: JSON config file controlling type filtering, naming, and post-generation hooks
+- **ViewModels**: Type Schema automatically transformed into template-friendly data structures
+
+Templates enable flexible code generation for any language or format (Go, Rust, GraphQL, documentation, configs) by describing the output format rather than implementing generation logic.
+
+**When to use**: Custom language support, quick prototyping, template-driven customization, non-code output
+
+---
+
 ## Roadmap
 
 - [x] TypeScript generation