Add automatic advice when folks hit one of two common but minor YAML gotchas, so…

Add automatic advice when folks hit one of two common but minor YAML gotchas, so they can be more easily correct them on their own.

CHANGELOG.md

@@ -7,9 +7,10 @@ Highlighted new features:
 
 * Added do-until feature, which can be used to retry a failed task a specified number of times with a delay in-between the retries.
 * (docs pending) Added failed_when option for tasks, which can be used to specify logical statements that make it easier to determine when a task has failed, or to make it easier to ignore certain non-zero return codes for some commands.
-* (docs pending) Added the "subelement" lookup plugin, which allows iteration of the keys of a dictionary or items in a list.
+* Added the "subelement" lookup plugin, which allows iteration of the keys of a dictionary or items in a list.
 * Added the capability to use either paramiko or ssh for the inital setup connection of an accelerated playbook.
 * (docs pending) Swap the active user on a task in the middle of a play with the 'remote_user' parameter.
+* Automatically provide advice on common parser errors users encounter.
 
 New modules:
 

lib/ansible/utils/__init__.py

@@ -336,6 +336,48 @@ def parse_yaml(data):
     ''' convert a yaml string to a data structure '''
     return smush_ds(yaml.safe_load(data))
 
+def process_common_errors(msg, probline, column):
+    replaced = probline.replace(" ","")
+    if replaced.find(":{{") != -1 and replaced.find("}}") != -1:
+        msg = msg + """
+This one looks easy to fix.  YAML thought it was looking for the start of a 
+hash/dictionary and was confused to see a second "{".  Most likely this was
+meant to be an ansible template evaluation instead, so we have to give the 
+parser a small hint that we wanted a string instead. The solution here is to 
+just quote the entire value.
+
+For instance, if the original line was:
+
+    app_path: {{ base_path }}/foo
+
+It should be written as:
+
+    app_path: "{{ base_path }}/foo"
+"""
+
+    elif len(probline) and probline[column] == ":" and probline.find("=") != -1:
+        msg = msg + """
+This one looks easy to fix.  There is an extra unquoted colon in the line 
+and this is confusing the parser. It was only expecting to find one free 
+colon. The solution is just add some quotes around the colon, or quote the 
+entire line after the first colon.
+
+For instance, if the original line was:
+
+    copy: src=file dest=/path/filename:with_colon.txt
+
+It can be written as:
+
+    copy: src=file dest='/path/filename:with_colon.txt'
+
+Or:
+    
+    copy: 'src=file dest=/path/filename:with_colon.txt'
+
+
+"""
+    return msg
+
 def process_yaml_error(exc, data, path=None):
     if hasattr(exc, 'problem_mark'):
         mark = exc.problem_mark
@@ -351,6 +393,10 @@ Note: The error may actually appear before this position: line %s, column %s
 %s
 %s
 %s""" % (path, mark.line + 1, mark.column + 1, before_probline, probline, arrow)
+
+        msg = process_common_errors(msg, probline, mark.column)
+
+
     else:
         # No problem markers means we have to throw a generic
         # "stuff messed up" type message. Sry bud.