Allow non-prefix files if prefix version missing

This fixes #5

== modules

Prefixed files are checked first and then fallback to non-prefixed
files.

== globs

All the matches are checked and if a prefixed version can't be found but
a non-prefixed version exists that match is used instead. Example:

--- _baz.css
--- bar.css
--- baz.css

Given the above list of files and `*.css` as the glob it would return
[`_baz.css`, `bar.css`]

Author: simonsmith

lib/resolve-glob.js

@@ -3,29 +3,51 @@ var globby = require('globby');
 var addPrefix = require('./add-prefix');
 var hasPrefix = require('./has-prefix');
 var hasExtensions = require('./has-extensions');
+var reduce = require('lodash/fp/reduce');
+var findIndex = require('lodash/fp/findIndex');
+var map = require('lodash/fp/map');
+var flow = require('lodash/fp/flow');
+var filter = require('lodash/fp/filter');
+
+function checkPrefixedVersionExists(fileToCheck, paths, prefix) {
+    var index = findIndex(p => {
+        const currentFile = path.basename(p);
+        return currentFile === prefix + fileToCheck;
+    }, paths);
+    return index === -1;
+}
 
 module.exports = function resolveGlob(id, base, opts) {
     var prefix = opts.prefix;
     var extensions = opts.extensions;
     var paths = [base].concat(opts.path);
-    var patterns = [];
     var prefixedId = prefix ? addPrefix(id, prefix) : null;
 
-    paths.forEach(function (p) {
-        [''].concat(extensions).forEach(function (ext) {
+    var patterns = reduce((acc, p) => {
+        [''].concat(extensions).forEach(ext => {
             if (prefix) {
-                patterns.push(path.resolve(p, prefixedId + ext));
+                acc.push(path.resolve(p, prefixedId + ext));
             }
-            patterns.push(path.resolve(p, id + ext));
+            acc.push(path.resolve(p, id + ext));
         });
-    });
+        return acc;
+    }, [], paths);
 
-    return globby(patterns).then(function (files) {
-        return files.filter(function (file) {
-            return hasExtensions(file, extensions) &&
-                (!prefix || hasPrefix(file, prefix));
-        }).map(function (file) {
-            return path.normalize(file);
+    return globby(patterns)
+        .then(files => {
+            return flow(
+                // Allows a file through if it has a prefix. If it doesn't have
+                // a prefix the current list of files are checked to see if a
+                // prefix version exists and if not it is added.
+                reduce((acc, item) => {
+                    var fileName = path.basename(item);
+                    if (hasPrefix(item, prefix) || checkPrefixedVersionExists(fileName, acc, prefix)) { // eslint-disable-line max-len
+                        acc.push(item);
+                    }
+                    return acc;
+                }, []),
+                filter(file => hasExtensions(file, extensions)),
+                map(file => path.normalize(file))
+            )(files);
         });
-    });
 };

lib/resolve-module.js

@@ -41,12 +41,13 @@ module.exports = function (id, base, opts) {
         }
     };
 
-    return resolve('./' + prefixedId, resolveOpts).catch(function () {
-        if (!prefix) {
-            throw Error();
-        }
-        return resolve(prefixedId, resolveOpts);
-    }).catch(function () {
-        return resolve(id, resolveOpts);
-    });
+    return resolve('./' + prefixedId, resolveOpts)
+        .catch(() => {
+            if (!prefix) {
+                throw Error();
+            }
+            return resolve(prefixedId, resolveOpts);
+        })
+        .catch(() => resolve('./' + id, resolveOpts))
+        .catch(() => resolve(id, resolveOpts));
 };

package.json

@@ -20,6 +20,7 @@
   "dependencies": {
     "globby": "^6.1.0",
     "is-glob": "^3.1.0",
+    "lodash": "^4.17.4",
     "object-assign": "^4.0.1",
     "pify": "^2.3.0",
     "postcss": "^5.0.15",