Improved the search by including a levenshtein distance calculation which enables the docs search function to be more forgiving for spelling mistakes

Author: jroweboy

src/librustdoc/html/static/main.js

@@ -58,7 +58,7 @@
             }
             $('#' + from)[0].scrollIntoView();
             $('.line-numbers span').removeClass('line-highlighted');
-            for (i = from; i <= to; i += 1) {
+            for (i = from; i <= to; ++i) {
                 $('#' + i).addClass('line-highlighted');
             }
         }
@@ -99,7 +99,7 @@
             stripped = '',
             len = rootPath.match(/\.\.\//g).length + 1;
 
-        for (i = 0; i < len; i += 1) {
+        for (i = 0; i < len; ++i) {
             match = url.match(/\/[^\/]*$/);
             if (i < len - 1) {
                 stripped = match[0] + stripped;
@@ -111,9 +111,44 @@
 
         document.location.href = url;
     });
+    /**
+     * Code from Stackoverflow to compute the Levenshtein distance between two strings
+     * Written by Marco de Wit at http://stackoverflow.com/a/18514751/745719
+     */
+    var levenshtein = (function() {
+        var row2 = [];
+        return function(s1, s2) {
+            if (s1 === s2) {
+                return 0;
+            } else {
+                var s1_len = s1.length, s2_len = s2.length;
+                if (s1_len && s2_len) {
+                    var i1 = 0, i2 = 0, a, b, c, c2, row = row2;
+                    while (i1 < s1_len)
+                        row[i1] = ++i1;
+                    while (i2 < s2_len) {
+                        c2 = s2.charCodeAt(i2);
+                        a = i2;
+                        ++i2;
+                        b = i2;
+                        for (i1 = 0; i1 < s1_len; ++i1) {
+                            c = a + (s1.charCodeAt(i1) !== c2 ? 1 : 0);
+                            a = row[i1];
+                            b = b < a ? (b < c ? b + 1 : c) : (a < c ? a + 1 : c);
+                            row[i1] = b;
+                        }
+                    }
+                    return b;
+                } else {
+                    return s1_len + s2_len;
+                }
+            }
+        };
+    })();
 
     function initSearch(rawSearchIndex) {
         var currentResults, index, searchIndex;
+        var MAX_LEV_DISTANCE = 3;
         var params = getQueryStringParams();
 
         // Populate search bar with query string search term when provided,
@@ -140,7 +175,7 @@
                 split = valLower.split("::");
 
             //remove empty keywords
-            for (var j = 0; j < split.length; j++) {
+            for (var j = 0; j < split.length; ++j) {
                 split[j].toLowerCase();
                 if (split[j] === "") {
                     split.splice(j, 1);
@@ -153,7 +188,7 @@
                 val.charAt(val.length - 1) === val.charAt(0))
             {
                 val = val.substr(1, val.length - 2);
-                for (var i = 0; i < nSearchWords; i += 1) {
+                for (var i = 0; i < nSearchWords; ++i) {
                     if (searchWords[i] === val) {
                         // filter type: ... queries
                         if (typeFilter < 0 || typeFilter === searchIndex[i].ty) {
@@ -167,15 +202,31 @@
             } else {
                 // gather matching search results up to a certain maximum
                 val = val.replace(/\_/g, "");
-                for (var i = 0; i < split.length; i++) {
-                    for (var j = 0; j < nSearchWords; j += 1) {
+                for (var i = 0; i < split.length; ++i) {
+                    for (var j = 0; j < nSearchWords; ++j) {
+                        var lev_distance;
                         if (searchWords[j].indexOf(split[i]) > -1 ||
                             searchWords[j].indexOf(val) > -1 ||
                             searchWords[j].replace(/_/g, "").indexOf(val) > -1)
                         {
                             // filter type: ... queries
                             if (typeFilter < 0 || typeFilter === searchIndex[j].ty) {
-                                results.push({id: j, index: searchWords[j].replace(/_/g, "").indexOf(val)});
+                                results.push({
+                                    id: j,
+                                    index: searchWords[j].replace(/_/g, "").indexOf(val),
+                                    lev: 0,
+                                });
+                            }
+                        } else if (
+                            (lev_distance = levenshtein(searchWords[j], val)) <= 
+                                MAX_LEV_DISTANCE) {
+                            if (typeFilter < 0 || typeFilter === searchIndex[j].ty) {
+                                results.push({
+                                    id: j,
+                                    index: 0,
+                                    // we want lev results to go lower than others
+                                    lev: lev_distance,
+                                });
                             }
                         }
                         if (results.length === max) {
@@ -186,7 +237,7 @@
             }
 
             var nresults = results.length;
-            for (var i = 0; i < nresults; i += 1) {
+            for (var i = 0; i < nresults; ++i) {
                 results[i].word = searchWords[results[i].id];
                 results[i].item = searchIndex[results[i].id] || {};
             }
@@ -198,6 +249,12 @@
             results.sort(function(aaa, bbb) {
                 var a, b;
 
+                // Sort by non levenshtein results and then levenshtein results by the distance
+                // (less changes required to match means higher rankings)
+                a = (aaa.lev);
+                b = (bbb.lev);
+                if (a !== b) return a - b;
+
                 // sort by crate (non-current crate goes later)
                 a = (aaa.item.crate !== window.currentCrate);
                 b = (bbb.item.crate !== window.currentCrate);
@@ -255,7 +312,7 @@
                     results[i].id = -1;
                 }
             }
-            for (var i = 0; i < results.length; i++) {
+            for (var i = 0; i < results.length; ++i) {
                 var result = results[i],
                     name = result.item.name.toLowerCase(),
                     path = result.item.path.toLowerCase(),
@@ -285,38 +342,23 @@
          * @return {[boolean]}       [Whether the result is valid or not]
          */
         function validateResult(name, path, keys, parent) {
-            //initially valid
-            var validate = true;
-            //if there is a parent, then validate against parent
-            if (parent !== undefined) {
-                for (var i = 0; i < keys.length; i++) {
-                    // if previous keys are valid and current key is in the
-                    // path, name or parent
-                    if ((validate) &&
-                        (name.toLowerCase().indexOf(keys[i]) > -1 ||
-                         path.toLowerCase().indexOf(keys[i]) > -1 ||
-                         parent.name.toLowerCase().indexOf(keys[i]) > -1))
-                    {
-                        validate = true;
-                    } else {
-                        validate = false;
-                    }
-                }
-            } else {
-                for (var i = 0; i < keys.length; i++) {
-                    // if previous keys are valid and current key is in the
-                    // path, name
-                    if ((validate) &&
-                        (name.toLowerCase().indexOf(keys[i]) > -1 ||
-                         path.toLowerCase().indexOf(keys[i]) > -1))
-                    {
-                        validate = true;
-                    } else {
-                        validate = false;
-                    }
+            for (var i=0; i < keys.length; ++i) {
+                // each check is for validation so we negate the conditions and invalidate
+                if (!( 
+                    // check for an exact name match
+                    name.toLowerCase().indexOf(keys[i]) > -1 ||
+                    // then an exact path match
+                    path.toLowerCase().indexOf(keys[i]) > -1 ||
+                    // next if there is a parent, check for exact parent match
+                    (parent !== undefined && 
+                        parent.name.toLowerCase().indexOf(keys[i]) > -1) ||
+                    // lastly check to see if the name was a levenshtein match
+                    levenshtein(name.toLowerCase(), keys[i]) <= 
+                        MAX_LEV_DISTANCE)) {
+                    return false;
                 }
             }
-            return validate;
+            return true;
         }
 
         function getQuery() {
@@ -496,7 +538,7 @@
 
             resultIndex = execQuery(query, 20000, index);
             len = resultIndex.length;
-            for (i = 0; i < len; i += 1) {
+            for (i = 0; i < len; ++i) {
                 if (resultIndex[i].id > -1) {
                     obj = searchIndex[resultIndex[i].id];
                     filterdata.push([obj.name, obj.ty, obj.path, obj.desc]);
@@ -568,7 +610,7 @@
                 // faster analysis operations
                 var len = items.length;
                 var lastPath = "";
-                for (var i = 0; i < len; i += 1) {
+                for (var i = 0; i < len; ++i) {
                     var rawRow = items[i];
                     var row = {crate: crate, ty: rawRow[0], name: rawRow[1],
                                path: rawRow[2] || lastPath, desc: rawRow[3],
@@ -640,7 +682,7 @@
                 crates.push(crate);
             }
             crates.sort();
-            for (var i = 0; i < crates.length; i++) {
+            for (var i = 0; i < crates.length; ++i) {
                 var klass = 'crate';
                 if (crates[i] == window.currentCrate) {
                     klass += ' current';
@@ -657,10 +699,10 @@
     window.register_implementors = function(imp) {
         var list = $('#implementors-list');
         var libs = Object.getOwnPropertyNames(imp);
-        for (var i = 0; i < libs.length; i++) {
+        for (var i = 0; i < libs.length; ++i) {
             if (libs[i] == currentCrate) continue;
             var structs = imp[libs[i]];
-            for (var j = 0; j < structs.length; j++) {
+            for (var j = 0; j < structs.length; ++j) {
                 var code = $('<code>').append(structs[j]);
                 $.each(code.find('a'), function(idx, a) {
                     var href = $(a).attr('href');