Sublime Text 2: trying to escape the dollar sign - autocomplete

Question

I'm trying to define a keybind in Sublime to have it autopair the dollar sign, "$", in the same way it autopairs the following symbols:
"
(
[
{
'
I opened the default keymap file and added the following code:
// Auto-pair dollar signs
{ "keys": ["\$"], "command": "insert_snippet", "args": {"contents": "\$$0\$"}, "context":
[
{ "key": "setting.auto_match_enabled", "operator": "equal", "operand": true },
{ "key": "selection_empty", "operator": "equal", "operand": true, "match_all": true },
{ "key": "following_text", "operator": "regex_contains", "operand": "^(?:\t| |\\)|]|\\}|>|$)", "match_all": true },
{ "key": "preceding_text", "operator": "not_regex_contains", "operand": "[\$a-zA-Z0-9_]$", "match_all": true },
{ "key": "eol_selector", "operator": "not_equal", "operand": "string.quoted.double", "match_all": true }
]
},
{ "keys": ["\$"], "command": "insert_snippet", "args": {"contents": "\$${0:$SELECTION}\$"}, "context":
[
{ "key": "setting.auto_match_enabled", "operator": "equal", "operand": true },
{ "key": "selection_empty", "operator": "equal", "operand": false, "match_all": true }
]
},
{ "keys": ["\$"], "command": "move", "args": {"by": "characters", "forward": true}, "context":
[
{ "key": "setting.auto_match_enabled", "operator": "equal", "operand": true },
{ "key": "selection_empty", "operator": "equal", "operand": true, "match_all": true },
{ "key": "following_text", "operator": "regex_contains", "operand": "^\$", "match_all": true }
]
},
{ "keys": ["backspace"], "command": "run_macro_file", "args": {"file": "Packages/Default/Delete Left Right.sublime-macro"}, "context":
[
{ "key": "setting.auto_match_enabled", "operator": "equal", "operand": true },
{ "key": "selection_empty", "operator": "equal", "operand": true, "match_all": true },
{ "key": "preceding_text", "operator": "regex_contains", "operand": "\$$", "match_all": true },
{ "key": "following_text", "operator": "regex_contains", "operand": "^\$", "match_all": true }
]
},
Notice the escaped dollar signs, \$. In the editor, they show up highlighted in red, and when I try to save the file, I get an invalid escape error message. What is the correct way of escaping the dollar sign?

Answer 1

Mind your escapes
You are going through two layers of programming here. First Python, then JSON. So, your escaped dollar signs actually need to be escaped twice:
"args": {"contents": "\\$$0\\$"}
After Sublime Text reads the settings file, Python will strip the first escape, leaving the following JSON representation
"args": {"contents": "\$$0\$"}
Then, once the JSON is parsed, you will finally end up with
"args": {"contents": "$$0$"}
Don't escape the keystroke
You don't need to escape $ in the keys list. The keystroke is a literal dollar sign, so no escaping is necessary
Here is how the first setting should look:
{ "keys": ["$"], "command": "insert_snippet", "args": {"contents": "\\$$0\\$"}, "context":
[
{ "key": "setting.auto_match_enabled", "operator": "equal", "operand": true },
{ "key": "selection_empty", "operator": "equal", "operand": true, "match_all": true },
{ "key": "following_text", "operator": "regex_contains", "operand": "^(?:\t| |\\)|]|\\}|>|$)", "match_all": true },
{ "key": "preceding_text", "operator": "not_regex_contains", "operand": "[\\$a-zA-Z0-9_]$", "match_all": true },
{ "key": "eol_selector", "operator": "not_equal", "operand": "string.quoted.double", "match_all": true }
]
},