google · yesudeep · May 5, 2025 · May 5, 2025
diff --git a/js/src/dotprompt.ts b/js/src/dotprompt.ts
@@ -20,18 +20,18 @@ import * as Handlebars from 'handlebars';
 import * as builtinHelpers from './helpers';
 import { parseDocument, toMessages } from './parse';
 import { picoschema } from './picoschema';
-import {
-  type DataArgument,
-  type JSONSchema,
-  type ParsedPrompt,
-  type PromptFunction,
-  type PromptMetadata,
-  type PromptStore,
-  type RenderedPrompt,
-  type Schema,
-  type SchemaResolver,
-  type ToolDefinition,
-  type ToolResolver,
+import type {
+  DataArgument,
+  JSONSchema,
+  ParsedPrompt,
+  PromptFunction,
+  PromptMetadata,
+  PromptStore,
+  RenderedPrompt,
+  Schema,
+  SchemaResolver,
+  ToolDefinition,
+  ToolResolver,
 } from './types';
 import { removeUndefinedFields } from './util';
 
@@ -196,6 +196,7 @@ export class Dotprompt {
       }
     );
 
+    // Create an instance of a PromptFunction.
     const renderFunc = async (
       data: DataArgument,
       options?: PromptMetadata<ModelConfig>
@@ -223,7 +224,10 @@ export class Dotprompt {
         messages: toMessages<ModelConfig>(renderedString, data),
       };
     };
+
+    // Add the parsed source to the prompt function as a property.
     (renderFunc as PromptFunction<ModelConfig>).prompt = parsedSource;
+
     return renderFunc as PromptFunction<ModelConfig>;
   }
 

diff --git a/python/dotpromptz/src/dotpromptz/dotprompt.py b/python/dotpromptz/src/dotpromptz/dotprompt.py
@@ -45,7 +45,7 @@
 import anyio
 
 from dotpromptz.helpers import BUILTIN_HELPERS
-from dotpromptz.parse import parse_document
+from dotpromptz.parse import parse_document, to_messages
 from dotpromptz.picoschema import picoschema_to_json_schema
 from dotpromptz.resolvers import resolve_json_schema, resolve_partial, resolve_tool
 from dotpromptz.typing import (
@@ -64,7 +64,7 @@
     VariablesT,
 )
 from dotpromptz.util import remove_undefined_fields
-from handlebarrz import EscapeFunction, Handlebars, HelperFn
+from handlebarrz import Context, EscapeFunction, Handlebars, HelperFn, RuntimeOptions
 
 # Pre-compiled regex for finding partial references in handlebars templates
 
@@ -117,7 +117,7 @@ def _identify_partials(template: str) -> set[str]:
     return set(_PARTIAL_PATTERN.findall(template))
 
 
-class CompiledRenderer(PromptFunction[ModelConfigT]):
+class RenderFunc(PromptFunction[ModelConfigT]):
     """A compiled prompt function with the prompt as a property.
 
     This is the Python equivalent of the renderFunc nested function
@@ -151,9 +151,42 @@ async def __call__(
         Returns:
             The rendered prompt.
         """
+        # Discard the input schema as once rendered it doesn't make sense.
+        merged_metadata: PromptMetadata[ModelConfigT] = await self._dotprompt.render_metadata(self.prompt, options)
+        merged_metadata.input = None
+
+        # Prepare input data, merging defaults from options if available.
+        context: Context = {
+            **((options.input.default or {}) if options and options.input else {}),
+            **(data.input if data.input is not None else {}),
+        }
+
+        # Prepare runtime options.
+        # TODO: options are currently ignored; need to add support for it.
+        runtime_options: RuntimeOptions = {
+            'data': {
+                'metadata': {
+                    'prompt': merged_metadata.model_dump(exclude_none=True, by_alias=True),
+                    'docs': data.docs,
+                    'messages': data.messages,
+                },
+                **(data.context or {}),
+            },
+        }
+
+        # Render the string.
+        render_string = self._handlebars.compile(self.prompt.template)
+        rendered_string = render_string(context, runtime_options)
+
+        # Parse the rendered string into messages.
+        messages = to_messages(rendered_string, data)
+
         # Construct and return the final RenderedPrompt.
-        # TODO: Stub
-        return RenderedPrompt[ModelConfigT](messages=[])
+        return RenderedPrompt[ModelConfigT](
+            # Spread the metadata fields into the RenderedPrompt constructor.
+            **merged_metadata.model_dump(exclude_none=True, by_alias=True),
+            messages=messages,
+        )
 
 
 class Dotprompt:
@@ -294,7 +327,7 @@ async def compile(
 
         # Resolve partials before compiling.
         await self._resolve_partials(prompt.template)
-        return CompiledRenderer(self, self._handlebars, prompt)
+        return RenderFunc(self, self._handlebars, prompt)
 
     async def render_metadata(
         self,
@@ -453,12 +486,13 @@ async def _resolve_tools(self, metadata: PromptMetadata[ModelConfigT]) -> Prompt
                 # Found locally.
                 out.tool_defs.append(self._tools[name])
             elif have_resolver:
-                # Resolve from the tool resolver.
+                # Resolve using the tool resolver.
                 to_resolve.append(name)
             else:
                 # Unregistered tool.
                 unregistered_names.append(name)
 
+        # Resolve all the tools to be resolved using the resolver.
         if to_resolve:
 
             async def resolve_and_append(tool_name: str) -> None:

diff --git a/python/handlebarrz/src/handlebarrz/__init__.py b/python/handlebarrz/src/handlebarrz/__init__.py
@@ -67,11 +67,13 @@ def format_name(params, hash, ctx):
 ```
 """
 
+from __future__ import annotations
+
 import json
 import sys  # noqa
 from collections.abc import Callable
 from pathlib import Path
-from typing import Any
+from typing import Any, TypedDict
 
 import structlog
 
@@ -91,6 +93,22 @@ def format_name(params, hash, ctx):
 
 HelperFn = Callable[[list[Any], dict[str, Any], dict[str, Any]], str]
 NativeHelperFn = Callable[[str, str, str], str]
+Context = dict[str, Any]
+
+
+class RuntimeOptions(TypedDict):
+    """Options for the runtime of a Handlebars template.
+
+    These options are used to configure the runtime behavior of a Handlebars
+    template. They can be passed to the compiled template function to customize
+    the rendering process.
+    """
+
+    data: dict[str, Any] | None
+    # TODO: Add other options based on supported features.
+
+
+CompiledRenderer = Callable[[Context, RuntimeOptions | None], str]
 
 
 class EscapeFunction(StrEnum):
@@ -427,7 +445,7 @@ def unregister_template(self, name: str) -> None:
         self._template.unregister_template(name)
         logger.debug({'event': 'template_unregistered', 'name': name})
 
-    def render(self, name: str, data: dict[str, Any]) -> str:
+    def render(self, name: str, data: dict[str, Any], options: RuntimeOptions | None = None) -> str:
         """Render a template with the given data.
 
         Renders a previously registered template using the provided data
@@ -437,6 +455,7 @@ def render(self, name: str, data: dict[str, Any]) -> str:
         Args:
             name: The name of the template to render
             data: The data to render the template with
+            options: Additional options for the template.
 
         Returns:
             str: The rendered template string
@@ -445,6 +464,8 @@ def render(self, name: str, data: dict[str, Any]) -> str:
             ValueError: If the template does not exist or there is a rendering
                 error.
         """
+        # TODO: options is currently ignored; need to add support for it.
+
         try:
             result = self._template.render(name, json.dumps(data))
             logger.debug({'event': 'template_rendered', 'name': name})
@@ -457,7 +478,7 @@ def render(self, name: str, data: dict[str, Any]) -> str:
             })
             raise
 
-    def render_template(self, template_string: str, data: dict[str, Any]) -> str:
+    def render_template(self, template_string: str, data: dict[str, Any], options: RuntimeOptions | None = None) -> str:
         """Render a template string directly without registering it.
 
         Parses and renders the template string in one step. This is useful for
@@ -467,6 +488,7 @@ def render_template(self, template_string: str, data: dict[str, Any]) -> str:
         Args:
             template_string: The template string to render
             data: The data to render the template with
+            options: Additional options for the template.
 
         Returns:
             Rendered template string.
@@ -475,8 +497,15 @@ def render_template(self, template_string: str, data: dict[str, Any]) -> str:
             ValueError: If there is a syntax error in the template or a
                 rendering error.
         """
+        # TODO: options is currently ignored; need to add support for it.
         try:
-            result = self._template.render_template(template_string, json.dumps(data))
+            # Serialize options if provided, focusing on the '@data' part
+            options_json = None
+            if options:
+                # Pass the whole options dict as JSON
+                options_json = json.dumps(options)
+
+            result = self._template.render_template(template_string, json.dumps(data), options_json)
             logger.debug({'event': 'template_string_rendered'})
             return result
         except ValueError as e:
@@ -486,7 +515,7 @@ def render_template(self, template_string: str, data: dict[str, Any]) -> str:
             })
             raise
 
-    def compile(self, template_string: str) -> Callable[[dict[str, Any]], str]:
+    def compile(self, template_string: str) -> CompiledRenderer:
         """Compile a template string into a reusable function.
 
         This method provides an interface similar to Handlebars.js's `compile`.
@@ -502,8 +531,8 @@ def compile(self, template_string: str) -> Callable[[dict[str, Any]], str]:
             template_string: The Handlebars template string to compile.
 
         Returns:
-            A callable function that takes a data dictionary and returns the
-            rendered string.
+            A callable function that takes a data dictionary and some runtime
+            options and returns the rendered string.
 
         Raises:
             ValueError: If there is a syntax error during the initial parse
@@ -512,8 +541,17 @@ def compile(self, template_string: str) -> Callable[[dict[str, Any]], str]:
             called.
         """
 
-        def compiled(data: dict[str, Any]) -> str:
-            return self.render_template(template_string, data)
+        def compiled(context: Context, options: RuntimeOptions | None = None) -> str:
+            """Compiled template function.
+
+            Args:
+                context: The data to render the template with.
+                options: Additional options for the template.
+
+            Returns:
+                The rendered template string.
+            """
+            return self.render_template(template_string, context, options)
 
         return compiled
 

diff --git a/python/handlebarrz/src/handlebarrz/_native.pyi b/python/handlebarrz/src/handlebarrz/_native.pyi
@@ -17,6 +17,7 @@
 """Stub type annotations for native Handlebars."""
 
 from collections.abc import Callable
+from typing import Any
 
 def html_escape(text: str) -> str: ...
 def no_escape(text: str) -> str: ...
@@ -52,7 +53,7 @@ class HandlebarrzTemplate:
 
     # Rendering.
     def render(self, name: str, data_json: str) -> str: ...
-    def render_template(self, template_str: str, data_json: str) -> str: ...
+    def render_template(self, template_str: str, data_json: str, options_json: str | None = None) -> str: ...
 
     # Extra helper registration.
     def register_extra_helpers(self) -> None: ...
diff --git a/python/handlebarrz/src/lib.rs b/python/handlebarrz/src/lib.rs
@@ -450,7 +450,8 @@ impl HandlebarrzTemplate {
     /// # Arguments
     ///
     /// * `template_string` - The template source code.
-    /// * `data` - The data to use for rendering (as JSON).
+    /// * `data_json` - The data to use for rendering (as JSON).
+    /// * `options_json` - Optional. If provided, the data will be merged with this JSON object.
     ///
     /// # Raises
     ///
@@ -459,11 +460,28 @@ impl HandlebarrzTemplate {
     /// # Returns
     ///
     /// Rendered template as a string.
-    #[pyo3(text_signature = "($self, template_string, data)")]
-    fn render_template(&self, template_string: &str, data: &str) -> PyResult<String> {
-        let data: Value = serde_json::from_str(data)
+    #[pyo3(text_signature = "($self, template_string, data_json, options_json = None)")]
+    fn render_template(
+        &self,
+        template_string: &str,
+        data_json: &str,
+        _options_json: Option<&str>,
+    ) -> PyResult<String> {
+        let data: Value = serde_json::from_str(data_json)
             .map_err(|e| PyValueError::new_err(format!("invalid JSON: {}", e)))?;
 
+        // TODO: Implement setting the data attribute of runtime options.
+        // if let Some(options_str) = options_json {
+        //     let options_data: Value = serde_json::from_str(options_str)
+        //         .map_err(|e| PyValueError::new_err(format!("invalid options JSON: {}", e)))?;
+
+        //     if let (Some(data_map), Some(_options_map)) =
+        //         (data.as_object_mut(), options_data.as_object())
+        //     {
+        //         data_map.insert("@data".to_string(), options_data.clone());
+        //     }
+        // }
+
         self.registry
             .render_template(template_string, &data)
             .map_err(|e| PyValueError::new_err(e.to_string()))