Take options parameter in anchoring methods

Rather than having each of the anchoring implementations have different
call signatures for their methods, use an options argument that varies
in content between the implementations, but probably shares some core
options like the root node.

h/static/scripts/annotator/guest.coffee

@@ -228,7 +228,9 @@ module.exports = class Guest extends Annotator
   # :rtype: Promise
   ####
   anchorTarget: (target) ->
-    root = @element[0]
+    options =
+      ignoreSelector: '[class^="annotator-"]'
+      root: @element[0]
 
     # Selectors
     fragment = null
@@ -253,9 +255,9 @@ module.exports = class Guest extends Annotator
 
     if fragment?
       promise = promise.catch =>
-        a = anchor.FragmentAnchor.fromSelector(fragment)
+        a = anchor.FragmentAnchor.fromSelector(fragment, options)
         Promise.resolve(a).then (a) ->
-          Promise.resolve(a.toRange(root)).then (r) ->
+          Promise.resolve(a.toRange(options)).then (r) ->
             if quote?.exact? and r.toString() != quote.exact
               throw new Error('quote mismatch')
             else
@@ -263,9 +265,9 @@ module.exports = class Guest extends Annotator
 
     if range?
       promise = promise.catch =>
-        a = anchor.RangeAnchor.fromSelector(range, root)
+        a = anchor.RangeAnchor.fromSelector(range, options)
         Promise.resolve(a).then (a) ->
-          Promise.resolve(a.toRange(root)).then (r) ->
+          Promise.resolve(a.toRange(options)).then (r) ->
             if quote?.exact? and r.toString() != quote.exact
               throw new Error('quote mismatch')
             else
@@ -273,9 +275,9 @@ module.exports = class Guest extends Annotator
 
     if position?
       promise = promise.catch =>
-        a = anchor.TextPositionAnchor.fromSelector(position)
+        a = anchor.TextPositionAnchor.fromSelector(position, options)
         Promise.resolve(a).then (a) ->
-          Promise.resolve(a.toRange(root)).then (r) ->
+          Promise.resolve(a.toRange(options)).then (r) ->
             if quote?.exact? and r.toString() != quote.exact
               throw new Error('quote mismatch')
             else
@@ -284,9 +286,9 @@ module.exports = class Guest extends Annotator
     if quote?
       promise = promise.catch =>
         # The quote is implicitly checked during range conversion.
-        a = anchor.TextQuoteAnchor.fromSelector(quote, position)
+        a = anchor.TextQuoteAnchor.fromSelector(quote, options)
         Promise.resolve(a).then (a) ->
-          Promise.resolve(a.toRange(root))
+          Promise.resolve(a.toRange(options))
 
     return promise
 
@@ -328,17 +330,21 @@ module.exports = class Guest extends Annotator
     return Promise.all(targets)
 
   createSelectors: (range) ->
-    root = @element[0]
-    toSelector = (anchor) -> anchor.toSelector(root)
-    softFail = (reason) -> null
-    notNull = (selectors) -> (s for s in selectors when s?)
+    options =
+      ignoreSelector: '[class^="annotator-"]'
+      root: @element[0]
+
+    notNull = (selectors) ->
+      (s for s in selectors when s?)
+
     selectors = ANCHOR_TYPES.map (type) =>
       try
-        Promise.resolve(type.fromRange(range)).then (a) ->
-          Promise.resolve(a.toSelector(root))
-        , softFail
+        Promise.resolve(type.fromRange(range, options)).then (a) ->
+          Promise.resolve(a.toSelector(options))
+        , -> null
       catch
         Promise.resolve()
+
     return Promise.all(selectors).then(notNull)
 
   onSuccessfulSelection: (event, immediate) ->

h/static/scripts/annotator/lib/anchor.coffee

@@ -7,7 +7,7 @@ Annotator = require('annotator')
 $ = Annotator.$
 xpathRange = Annotator.Range
 
-textWalker = require('./text-walker')
+seek = require('dom-seek')
 
 
 # Helper functions for throwing common errors
@@ -82,7 +82,8 @@ class RangeAnchor extends Anchor
     return new RangeAnchor(range)
 
   # Create and anchor using the saved Range selector.
-  @fromSelector: (selector, root=document.body) ->
+  @fromSelector: (selector, options = {}) ->
+    root = options.root or document.body
     data = {
       start: selector.startContainer
       startOffset: selector.startOffset
@@ -95,7 +96,9 @@ class RangeAnchor extends Anchor
   toRange: ->
     return @range
 
-  toSelector: (root=document.body, ignoreSelector='[class^="annotator-"]') ->
+  toSelector: (options = {}) ->
+    root = options.root or document.body
+    ignoreSelector = options.ignoreSelector
     range = new xpathRange.BrowserRange(@range).serialize(root, ignoreSelector)
     return {
       type: 'RangeSelector'
@@ -120,7 +123,10 @@ class TextPositionAnchor extends Anchor
     unless @start? then missingParameter('start')
     unless @end? then missingParameter('end')
 
-  @fromRange: (range, root=document.body, filter=null) ->
+  @fromRange: (range, options = {}) ->
+    root = options.root or document.body
+    filter = options.filter or null
+
     range = new xpathRange.BrowserRange(range).normalize(root)
     walker = new textWalker.TextWalker(root, filter)
 
@@ -135,7 +141,10 @@ class TextPositionAnchor extends Anchor
   @fromSelector: (selector) ->
     return new TextPositionAnchor(selector.start, selector.end)
 
-  toRange: (root=document.body, filter=null) ->
+  toRange: (options = {}) ->
+    root = options.root or document.body
+    filter = options.filter or null
+
     walker = new textWalker.TextWalker(root, filter)
     range = document.createRange()
 
@@ -171,7 +180,10 @@ class TextQuoteAnchor extends Anchor
   constructor: (@quote, @prefix='', @suffix='', @start, @end) ->
     unless @quote? then missingParameter('quote')
 
-  @fromRange: (range, root=document.body, filter=null) ->
+  @fromRange: (range, options = {}) ->
+    root = options.root or document.body
+    filter = options.filter or null
+
     range = new xpathRange.BrowserRange(range).normalize(root)
     walker = new textWalker.TextWalker(root, filter)
 
@@ -190,22 +202,22 @@ class TextQuoteAnchor extends Anchor
 
     return new TextQuoteAnchor(exact, prefix, suffix, start, end)
 
-  @fromSelector: (selector, position) ->
+  @fromSelector: (selector, options = {}) ->
+    {start, end} = options.position ? {}
     {exact, prefix, suffix} = selector
-    {start, end} = position ? {}
     return new TextQuoteAnchor(exact, prefix, suffix, start, end)
 
-  toRange: (root=document.body) ->
+  toRange: (options = {}) ->
+    root = options.root or document.body
     corpus = root.textContent
     matcher = new DomTextMatcher(-> corpus)
 
-    options =
-      matchDistance: corpus.length * 2
-      contextMatchDistance: corpus.length * 2
-      contextMatchThreshold: 0.5
-      patternMatchThreshold: 0.5
-      flexContext: true
-      withFuzzyComparison: true
+    options.matchDistance ?= corpus.length * 2
+    options.contextMatchDistance ?= corpus.length * 2
+    options.contextMatchThreshold ?= 0.5
+    options.patternMatchThreshold ?= 0.5
+    options.flexContext ?= true
+    options.withFuzzyComparison ?= true
 
     if @prefix.length and @suffix.length
       result = matcher.searchFuzzyWithContext(