Fix Recaptcha rendering on dynamic forms

test.py

@@ -0,0 +1,16 @@
+from flask import Flask
+from flask_wtf import FlaskForm, RecaptchaField
+app = Flask(__name__)
+app.config['WTF_CSRF_ENABLED'] = False
+app.config['RECAPTCHA_PUBLIC_KEY'] = 'test'
+app.config['RECAPTCHA_PRIVATE_KEY'] = 'test'
+
+class F(FlaskForm):
+    r = RecaptchaField()
+
+with app.app_context():
+    f = F()
+    try:
+        print(f.r(class_="form-control"))
+    except Exception as e:
+        print("ERROR:", e)

test2.py

@@ -0,0 +1,13 @@
+from flask import Flask
+from flask_wtf import FlaskForm, RecaptchaField
+app = Flask(__name__)
+app.config['WTF_CSRF_ENABLED'] = False
+app.config['RECAPTCHA_PUBLIC_KEY'] = 'test'
+app.config['RECAPTCHA_PRIVATE_KEY'] = 'test'
+
+class F(FlaskForm):
+    r = RecaptchaField()
+
+with app.app_context():
+    f = F()
+    print("type:", f.r.type)

test3.py

@@ -0,0 +1,30 @@
+from flask import Flask, render_template_string
+from flask_wtf import FlaskForm, RecaptchaField
+from wtforms import StringField
+
+app = Flask(__name__)
+app.config['WTF_CSRF_ENABLED'] = False
+app.config['RECAPTCHA_PUBLIC_KEY'] = 'test'
+app.config['RECAPTCHA_PRIVATE_KEY'] = 'test'
+
+class F(FlaskForm):
+    name = StringField("name")
+    recaptcha = RecaptchaField()
+
+template = """
+{% macro render_input(field) %}
+  INPUT: {{ field(class_="form-control") }}
+{% endmacro %}
+
+{% for field in form %}
+  {% if field.type == "RecaptchaField" %}
+     {{ field }}
+  {% else %}
+     {{ render_input(field) }}
+  {% endif %}
+{% endfor %}
+"""
+
+with app.app_context():
+    f = F()
+    print(render_template_string(template, form=f))

test4.py

@@ -0,0 +1,26 @@
+from flask import Flask, render_template_string
+from flask_wtf import FlaskForm, RecaptchaField
+from wtforms import StringField
+
+app = Flask(__name__)
+app.config['WTF_CSRF_ENABLED'] = False
+app.config['RECAPTCHA_PUBLIC_KEY'] = 'test'
+app.config['RECAPTCHA_PRIVATE_KEY'] = 'test'
+
+class F(FlaskForm):
+    name = StringField("name")
+    recaptcha = RecaptchaField()
+
+template = """
+{% macro render_input(field) %}
+  INPUT: {{ field(class_="form-control") }}
+{% endmacro %}
+
+{% for field in form %}
+  {{ render_input(field) }}
+{% endfor %}
+"""
+
+with app.app_context():
+    f = F()
+    print(render_template_string(template, form=f))