Add documentation for function and config variable order

Closes #84

doc/AutoPairs.txt

@@ -1584,6 +1584,21 @@ raw keys, which can and will cause conflicts with typed letters if given the
 opportunity. Should you choose not to, though, you get to live with the
 consequences, if any.
 
+WARNING: This variable must be declared before calling any auto-pairs
+functions. See |autopairs-config-changes-broken| for more details.
+
+TL;DR: 
+Correct: >
+    let g:AutoPairsPrefix = '<some keybind here>'
+    let g:AutoPairs = autopairs#AutoPairsDefine({ ... some definitions here })
+<
+Incorrect: >
+    let g:AutoPairs = autopairs#AutoPairsDefine({ ... some definitions here })
+    let g:AutoPairsPrefix = '<some keybind here>'
+<
+
+Note that this applies to any of auto-pairs' functions.
+
 ------------------------------------------------------------------------------
                                              *g:AutoPairsDefaultDisableKeybinds*
 
@@ -1713,6 +1728,9 @@ don't want to use the standards, go ahead and omit this function.
 Additionally, if you want to add new types after loading, you need to use
 |autopairs#AutoPairsMap()|
 
+WARNING: Functions must be called after config variable declarations. See
+|autopairs-config-changes-broken|
+
 ------------------------------------------------------------------------------
 AutoPairsDefine()          *autopairs#AutoPairsDefine()* *autopairs-copy-defaults*
 Arguments: (pairs[, pairs_to_remove])
@@ -1739,6 +1757,10 @@ files are loaded when `autopair#` functions are called. This means using, for
 an instance, `autopairs#AutoPairsDefine` loads the file and makes the function
 valid.
 
+WARNING: Functions must be called after config variable declarations. This
+means g:AutoPairs has to be the variable defined last in many cases. See
+|autopairs-config-changes-broken| for more information
+
 ------------------------------------------------------------------------------
 AutoPairsMap()                     *autopairs#AutoPairsMap()* *auto-pairs-map-key*
 Arguments: (key)

doc/AutoPairsTrouble.txt

@@ -24,6 +24,7 @@ Table of Contents                           *autopairs-troubleshooting-contents*
     7. Test failures (and related errors) ... |autopairs-test-failures|
         1. Autocmd and syntax errors ........ |autopairs-typescript-errors|
     8. Weird auto-pairs stuff on <CR> ....... |autopairs-bad-cr|
+    9. Config changes not taking effect ..... |autopairs-config-changes-broken|
 
 ==============================================================================
 1. General troubleshooting                           *autopairs-troubleshooting-general*
@@ -373,4 +374,57 @@ the last straw for the other plugin, you can uninstall the other plugin plugin.
 
     See also |autopairs-autocomplete-cr|
 
+==============================================================================
+9. Config changes not taking effect            *autopairs-config-changes-broken*
+
+TL;DR:~
+
+Correct: >
+    let g:AutoPairsPrefix = '<some keybind here>'
+    let g:AutoPairs = autopairs#AutoPairsDefine({ ... some definitions here })
+<
+Incorrect: >
+    let g:AutoPairs = autopairs#AutoPairsDefine({ ... some definitions here })
+    let g:AutoPairsPrefix = '<some keybind here>'
+<
+This applies to any of auto-pairs' functions, generally identified by the
+`autopairs#` prefix.
+
+Long version~
+If you're making changes to auto-pairs' config variables and seeing it not
+take effect, you're probably running into an initialisation order problem.
+This particularly applies to |g:AutoPairsPrefix|, but may exist in other
+places as well. To avoid running into these problems, it's recommended to
+initialise variables before calling any of auto-pairs' functions.
+
+If any functions are called before variables are declared, this results in
+certain internal variables being initialised in a way that makes it difficult
+to change afterwards. Taking |g:AutoPairsPrefix| as an example, consider: >
+    let g:AutoPairs = autopairs#AutoPairsDefine({ ... some definitions here })
+    let g:AutoPairsPrefix = '<some keybind here>'
+<
+
+In this case, all the defaults are initialised after the g:AutoPairsDefine
+call. While this usually isn't a problem, all the keybind initialisations
+depend on the value of |g:AutoPairsPrefix|. Because it isn't defined prior to
+the function call, the function defines it as the default value. When
+|g:AutoPairsPrefix| then is defined after the function call, the variable
+initialisation function is not called again (and even if it was, it would
+not change anything, as the dependent variables are assumed to be initialised
+by the user, and won't be reinitialised).
+
+Simply put, if you're seeing this problem, it's caused by variables depending
+on other variables during initialisation, and the value of the variable is
+copied at the time of initialisation.
+
+This means that, as the TL;DR: stated, you need to call `autopairs#` functions
+after initialising the variables you're interested in, and not before. That
+way, when the variable initialisation happens, dependent variables are
+initialised correctly.
+
+See also~
+* https://github.com/LunarWatcher/auto-pairs/issues/84
+  The issue also contains a practical demonstration of this happening in
+  practice.
+
 vim:ft=help