Repository: getmoto/moto (python)

Issue:
error when template contains Iteration of list
Error existe in lastest version moto 4.0.8

Having this template : 
`{{#each items}} <a href="{{itemName}}">{{itemDesc}}</a> {{/each}}`

And our input : 

`{"items": [{"itemName": "item1", "itemDesc": "description 1"}]}`

Moto will not find out "items" from input because moto search for "#each items".

`def are_all_variables_present(template, template_data):`

https://github.com/spulec/moto/blob/80ab997010f9f8a2c26272671e6216ad12fac5c3/moto/ses/models.py#L115

In addition, moto can not find itemName and itemDesc from a lower level dict inside a list.

Pull request description:
SES: Improve template parsing
Fixes #5594 

Improves generation of SES templates to also support for-each loops.

AWS supports a subset of the Handlebars templates. There is a python-fork that could be used to parse SES templates here: https://github.com/wbond/pybars3

However, it is unmaintained and slow (with an import time of about 400ms). That's why I chose instead to write a custom parser, reusing an existing tokenizer used in DynamoDB.

Patch:
diff --git a/moto/dynamodb/parsing/key_condition_expression.py b/moto/dynamodb/parsing/key_condition_expression.py
index cb9953450..3bdbaa7e1 100644
--- a/moto/dynamodb/parsing/key_condition_expression.py
+++ b/moto/dynamodb/parsing/key_condition_expression.py
@@ -1,70 +1,6 @@
 from enum import Enum
 from moto.dynamodb.exceptions import MockValidationException
-
-
-class KeyConditionExpressionTokenizer:
-    """
-    Tokenizer for a KeyConditionExpression. Should be used as an iterator.
-    The final character to be returned will be an empty string, to notify the caller that we've reached the end.
-    """
-
-    def __init__(self, expression):
-        self.expression = expression
-        self.token_pos = 0
-
-    def __iter__(self):
-        self.token_pos = 0
-        return self
-
-    def is_eof(self):
-        return self.peek() == ""
-
-    def peek(self):
-        """
-        Peek the next character without changing the position
-        """
-        try:
-            return self.expression[self.token_pos]
-        except IndexError:
-            return ""
-
-    def __next__(self):
-        """
-        Returns the next character, or an empty string if we've reached the end of the string.
-        Calling this method again will result in a StopIterator
-        """
-        try:
-            result = self.expression[self.token_pos]
-            self.token_pos += 1
-            return result
-        except IndexError:
-            if self.token_pos == len(self.expression):
-                self.token_pos += 1
-                return ""
-            raise StopIteration
-
-    def skip_characters(self, phrase, case_sensitive=False) -> None:
-        """
-        Skip the characters in the supplied phrase.
-        If any other character is encountered instead, this will fail.
-        If we've already reached the end of the iterator, this will fail.
-        """
-        for ch in phrase:
-            if case_sensitive:
-                assert self.expression[self.token_pos] == ch
-            else:
-                assert self.expression[self.token_pos] in [ch.lower(), ch.upper()]
-            self.token_pos += 1
-
-    def skip_white_space(self):
-        """
-        Skip the any whitespace characters that are coming up
-        """
-        try:
-            while self.peek() == " ":
-                self.token_pos += 1
-        except IndexError:
-            pass
+from moto.utilities.tokenizer import GenericTokenizer
 
 
 class EXPRESSION_STAGES(Enum):
@@ -100,7 +36,7 @@ def parse_expression(
     key_name = comparison = None
     key_values = []
     results = []
-    tokenizer = KeyConditionExpressionTokenizer(key_condition_expression)
+    tokenizer = GenericTokenizer(key_condition_expression)
     for crnt_char in tokenizer:
         if crnt_char == " ":
             if current_stage == EXPRESSION_STAGES.INITIAL_STAGE:
diff --git a/moto/ses/models.py b/moto/ses/models.py
index 7227abe12..27e1e5fef 100644
--- a/moto/ses/models.py
+++ b/moto/ses/models.py
@@ -1,4 +1,3 @@
-import re
 import json
 import email
 import datetime
@@ -23,9 +22,9 @@ from .exceptions import (
     RuleSetNameAlreadyExists,
     RuleSetDoesNotExist,
     RuleAlreadyExists,
-    MissingRenderingAttributeException,
     ConfigurationSetAlreadyExists,
 )
+from .template import parse_template
 from .utils import get_random_message_id, is_valid_address
 from .feedback import COMMON_MAIL, BOUNCE, COMPLAINT, DELIVERY
 
@@ -106,17 +105,6 @@ class SESQuota(BaseModel):
         return self.sent
 
 
-def are_all_variables_present(template, template_data):
-    subject_part = template["subject_part"]
-    text_part = template["text_part"]
-    html_part = template["html_part"]
-
-    for var in re.findall("{{(.+?)}}", subject_part + text_part + html_part):
-        if not template_data.get(var):
-            return var, False
-    return None, True
-
-
 class SESBackend(BaseBackend):
     """
     Responsible for mocking calls to SES.
@@ -469,18 +457,13 @@ class SESBackend(BaseBackend):
                 "Template rendering data is invalid"
             )
 
-        var, are_variables_present = are_all_variables_present(template, template_data)
-        if not are_variables_present:
-            raise MissingRenderingAttributeException(var)
-
         subject_part = template["subject_part"]
         text_part = template["text_part"]
         html_part = template["html_part"]
 
-        for key, value in template_data.items():
-            subject_part = str.replace(str(subject_part), "{{" + key + "}}", value)
-            text_part = str.replace(str(text_part), "{{" + key + "}}", value)
-            html_part = str.replace(str(html_part), "{{" + key + "}}", value)
+        subject_part = parse_template(str(subject_part), template_data)
+        text_part = parse_template(str(text_part), template_data)
+        html_part = parse_template(str(html_part), template_data)
 
         email_obj = MIMEMultipart("alternative")
 
diff --git a/moto/ses/template.py b/moto/ses/template.py
new file mode 100644
index 000000000..ec34cd19c
--- /dev/null
+++ b/moto/ses/template.py
@@ -0,0 +1,45 @@
+from .exceptions import MissingRenderingAttributeException
+from moto.utilities.tokenizer import GenericTokenizer
+
+
+def parse_template(template, template_data, tokenizer=None, until=None):
+    tokenizer = tokenizer or GenericTokenizer(template)
+    state = ""
+    parsed = ""
+    var_name = ""
+    for char in tokenizer:
+        if until is not None and (char + tokenizer.peek(len(until) - 1)) == until:
+            return parsed
+        if char == "{":
+            tokenizer.skip_characters("{")
+            tokenizer.skip_white_space()
+            if tokenizer.peek() == "#":
+                state = "LOOP"
+                tokenizer.skip_characters("#each")
+                tokenizer.skip_white_space()
+            else:
+                state = "VAR"
+            continue
+        if char == "}":
+            if state in ["LOOP", "VAR"]:
+                tokenizer.skip_characters("}")
+                if state == "VAR":
+                    if template_data.get(var_name) is None:
+                        raise MissingRenderingAttributeException(var_name)
+                    parsed += template_data.get(var_name)
+                else:
+                    current_position = tokenizer.token_pos
+                    for item in template_data.get(var_name, []):
+                        tokenizer.token_pos = current_position
+                        parsed += parse_template(
+                            template, item, tokenizer, until="{{/each}}"
+                        )
+                        tokenizer.skip_characters("{/each}}")
+                var_name = ""
+                state = ""
+                continue
+        if state in ["LOOP", "VAR"]:
+            var_name += char
+            continue
+        parsed += char
+    return parsed
diff --git a/moto/utilities/tokenizer.py b/moto/utilities/tokenizer.py
new file mode 100644
index 000000000..a6e76dc7f
--- /dev/null
+++ b/moto/utilities/tokenizer.py
@@ -0,0 +1,62 @@
+class GenericTokenizer:
+    """
+    Tokenizer for a KeyConditionExpression. Should be used as an iterator.
+    The final character to be returned will be an empty string, to notify the caller that we've reached the end.
+    """
+
+    def __init__(self, expression):
+        self.expression = expression
+        self.token_pos = 0
+
+    def __iter__(self):
+        return self
+
+    def is_eof(self):
+        return self.peek() == ""
+
+    def peek(self, length=1):
+        """
+        Peek the next character without changing the position
+        """
+        try:
+            return self.expression[self.token_pos : self.token_pos + length]
+        except IndexError:
+            return ""
+
+    def __next__(self):
+        """
+        Returns the next character, or an empty string if we've reached the end of the string.
+        Calling this method again will result in a StopIterator
+        """
+        try:
+            result = self.expression[self.token_pos]
+            self.token_pos += 1
+            return result
+        except IndexError:
+            if self.token_pos == len(self.expression):
+                self.token_pos += 1
+                return ""
+            raise StopIteration
+
+    def skip_characters(self, phrase, case_sensitive=False) -> None:
+        """
+        Skip the characters in the supplied phrase.
+        If any other character is encountered instead, this will fail.
+        If we've already reached the end of the iterator, this will fail.
+        """
+        for ch in phrase:
+            if case_sensitive:
+                assert self.expression[self.token_pos] == ch
+            else:
+                assert self.expression[self.token_pos] in [ch.lower(), ch.upper()]
+            self.token_pos += 1
+
+    def skip_white_space(self):
+        """
+        Skip any whitespace characters that are coming up
+        """
+        try:
+            while self.peek() == " ":
+                self.token_pos += 1
+        except IndexError:
+            pass


Test patch:
diff --git a/tests/test_ses/test_ses_boto3.py b/tests/test_ses/test_ses_boto3.py
index c2c27cdb9..0ca55c7f8 100644
--- a/tests/test_ses/test_ses_boto3.py
+++ b/tests/test_ses/test_ses_boto3.py
@@ -1268,6 +1268,35 @@ def test_render_template():
     )
 
 
+@mock_ses
+def test_render_template__with_foreach():
+    conn = boto3.client("ses", region_name="us-east-1")
+
+    kwargs = dict(
+        TemplateName="MTT",
+        TemplateData=json.dumps(
+            {
+                "items": [
+                    {"type": "dog", "name": "bobby"},
+                    {"type": "cat", "name": "pedro"},
+                ]
+            }
+        ),
+    )
+
+    conn.create_template(
+        Template={
+            "TemplateName": "MTT",
+            "SubjectPart": "..",
+            "TextPart": "..",
+            "HtmlPart": "{{#each items}} {{name}} is a {{type}}, {{/each}}",
+        }
+    )
+    result = conn.test_render_template(**kwargs)
+    result["RenderedTemplate"].should.contain("bobby is a dog")
+    result["RenderedTemplate"].should.contain("pedro is a cat")
+
+
 @mock_ses
 def test_update_ses_template():
     conn = boto3.client("ses", region_name="us-east-1")
diff --git a/tests/test_ses/test_templating.py b/tests/test_ses/test_templating.py
new file mode 100644
index 000000000..0883013b0
--- /dev/null
+++ b/tests/test_ses/test_templating.py
@@ -0,0 +1,26 @@
+from moto.ses.template import parse_template
+import sure  # noqa # pylint: disable=unused-import
+
+
+def test_template_without_args():
+    parse_template("some template", template_data={}).should.equal("some template")
+
+
+def test_template_with_simple_arg():
+    t = "Dear {{name}},"
+    parse_template(t, template_data={"name": "John"}).should.equal("Dear John,")
+
+
+def test_template_with_foreach():
+    t = "List:{{#each l}} - {{obj}}{{/each}} and other things"
+    kwargs = {"l": [{"obj": "it1"}, {"obj": "it2"}]}
+    parse_template(t, kwargs).should.equal("List: - it1 - it2 and other things")
+
+
+def test_template_with_multiple_foreach():
+    t = "{{#each l}} - {{obj}}{{/each}} and list 2 {{#each l2}} {{o1}} {{o2}} {{/each}}"
+    kwargs = {
+        "l": [{"obj": "it1"}, {"obj": "it2"}],
+        "l2": [{"o1": "ob1", "o2": "ob2"}, {"o1": "oc1", "o2": "oc2"}],
+    }
+    parse_template(t, kwargs).should.equal(" - it1 - it2 and list 2  ob1 ob2  oc1 oc2 ")