Add support of Jinja code blocks (#183)

Author: mandel

docs/tutorial.md

@@ -305,7 +305,7 @@ Bob lives at the following address:
 
 ##  Calling code
 
-The following script shows how to execute python code ([file](https://github.com/IBM/prompt-declaration-language//blob/main/examples/tutorial/calling_code.pdl)). The python code is executed locally (or in a containerized way if using `pdl --sandbox`).  In principle, PDL is agnostic of any specific programming language, but we currently only support Python. Variables defined in PDL are copied into the global scope of the Python code, so those variables can be used directly in the code. However, mutating variables in Python has no effect on the variables in the PDL program. The result of the code must be assigned to the variable `result` internally to be propagated to the result of the block. A variable `def` on the code block will then be set to this result.
+The following script shows how to execute python code ([file](https://github.com/IBM/prompt-declaration-language//blob/main/examples/tutorial/calling_code.pdl)). The python code is executed locally (or in a containerized way if using `pdl --sandbox`).  In principle, PDL is agnostic of any specific programming language, but we currently only support Python, Jinja, and shell commands. Variables defined in PDL are copied into the global scope of the Python code, so those variables can be used directly in the code. However, mutating variables in Python has no effect on the variables in the PDL program. The result of the code must be assigned to the variable `result` internally to be propagated to the result of the block. A variable `def` on the code block will then be set to this result.
 
 In order to define variables that are carried over to the next Python code block, a special variable `PDL_SESSION` can be used, and
 variables assigned to it as fields.

examples/hello/hello-code-command.pdl

@@ -0,0 +1,4 @@
+description: Hello world showing call out to shell command
+lang: command
+code: |
+  echo "Hello World!"

examples/hello/hello-code-jinja.pdl

@@ -0,0 +1,6 @@
+description: Hello world showing call out to shell command
+defs:
+  world: "World"
+lang: jinja
+code: |
+  Hello {{ world }}!

pdl-live/src/pdl_ast.d.ts

@@ -2322,7 +2322,7 @@ export type Kind15 = "code";
  * Programming language of the code.
  *
  */
-export type Lang = "python" | "command";
+export type Lang = "python" | "command" | "jinja";
 /**
  * Code to execute.
  *

src/pdl/pdl-schema.json

@@ -2691,7 +2691,8 @@
           "description": "Programming language of the code.\n    ",
           "enum": [
             "python",
-            "command"
+            "command",
+            "jinja"
           ],
           "title": "Lang",
           "type": "string"

src/pdl/pdl_ast.py

@@ -281,7 +281,7 @@ class CodeBlock(Block):
     """Execute a piece of code."""
 
     kind: Literal[BlockKind.CODE] = BlockKind.CODE
-    lang: Literal["python", "command"]
+    lang: Literal["python", "command", "jinja"]
     """Programming language of the code.
     """
     code: "BlocksType"

src/pdl/pdl_interpreter.py

@@ -1261,8 +1261,18 @@ def step_call_code(
                     loc=loc,
                     trace=block.model_copy(update={"code": code_s}),
                 ) from exc
+        case "jinja":
+            try:
+                result = call_jinja(code_s, scope)
+                background = [{"role": state.role, "content": result}]
+            except Exception as exc:
+                raise PDLRuntimeError(
+                    f"Code error: {repr(exc)}",
+                    loc=loc,
+                    trace=block.model_copy(update={"code": code_s}),
+                ) from exc
         case _:
-            message = f"Unsupported language: {block.lan}"
+            message = f"Unsupported language: {block.lang}"
             raise PDLRuntimeError(
                 message,
                 loc=loc,
@@ -1300,6 +1310,14 @@ def call_command(code: str) -> str:
     return output
 
 
+def call_jinja(code: str, scope: dict) -> Any:
+    template = Template(
+        code,
+    )
+    result = template.render(scope)
+    return result
+
+
 def step_call(
     state: InterpreterState, scope: ScopeType, block: CallBlock, loc: LocationType
 ) -> Generator[YieldMessage, Any, tuple[Any, Messages, ScopeType, CallBlock]]:

tests/results/examples/hello/hello-code-command.result

@@ -0,0 +1,2 @@
+Hello World!
+

tests/results/examples/hello/hello-code-jinja.result

@@ -0,0 +1 @@
+Hello World!

tests/test_code.py

@@ -1,3 +1,4 @@
+from pdl.pdl import exec_str
 from pdl.pdl_ast import Program
 from pdl.pdl_interpreter import InterpreterState, empty_scope, process_prog
 
@@ -71,3 +72,54 @@ def test_command():
     document, _, scope, _ = process_prog(state, empty_scope, data)
     assert document == "Hello World!"
     assert scope["world"] == "World"
+
+
+def test_jinja1():
+    prog_str = """
+defs:
+  world: "World"
+lang: jinja
+code: |
+  Hello {{ world }}!
+"""
+    result = exec_str(prog_str)
+    assert result == "Hello World!"
+
+
+def test_jinja2():
+    prog_str = """
+defs:
+  world: "World"
+lang: jinja
+code: |
+  Hello ${ world }!
+"""
+    result = exec_str(prog_str)
+    assert result == "Hello World!"
+
+
+def test_jinja3():
+    prog_str = """
+defs:
+  scores:
+    array:
+    - 10
+    - 90
+    - 50
+    - 60
+    - 100
+lang: jinja
+code: |
+    {% for score in scores %}
+        {% if score > 80 %}good{% else %}bad{% endif %}{% endfor %}
+"""
+    result = exec_str(prog_str)
+    assert (
+        result
+        == """
+    bad
+    good
+    bad
+    bad
+    good"""
+    )