Decouple the graph and render logic from the fs watcher

This logic is all tightly coupled in the bin. This logic has been
notoriously impossible to test due to weird fs timing issues. By
extracting the actual logic we're now able to test it in isolation.

With this in place replacing Gaze (sass#636) becomes a viable option.
This PR not only massively increases our test coverage for the
watcher but also address a bunch of known edge cases i.e. orphaned
imports when a files is deleted.

Closes sass#1896
Fixes sass#1891

bin/node-sass

@@ -3,13 +3,13 @@
 var Emitter = require('events').EventEmitter,
   forEach = require('async-foreach').forEach,
   Gaze = require('gaze'),
-  grapher = require('sass-graph'),
   meow = require('meow'),
   util = require('util'),
   path = require('path'),
   glob = require('glob'),
   sass = require('../lib'),
   render = require('../lib/render'),
+  watcher = require('../lib/watcher'),
   stdout = require('stdout-stream'),
   stdin = require('get-stdin'),
   fs = require('fs');
@@ -229,63 +229,41 @@ function getOptions(args, options) {
  */
 
 function watch(options, emitter) {
-  var buildGraph = function(options) {
-    var graph;
-    var graphOptions = {
-      loadPaths: options.includePath,
-      extensions: ['scss', 'sass', 'css']
-    };
-
-    if (options.directory) {
-      graph = grapher.parseDir(options.directory, graphOptions);
-    } else {
-      graph = grapher.parseFile(options.src, graphOptions);
-    }
+  var handler = function(files) {
+    files.added.forEach(function(file) {
+      var watch = gaze.watched();
+      if (watch.indexOf(file) === -1) {
+        gaze.add(file);
+      }
+    });
 
-    return graph;
+    files.changed.forEach(function(file) {
+      if (path.basename(file)[0] !== '_') {
+        renderFile(file, options, emitter);
+      }
+    });
+
+    files.removed.forEach(function(file) {
+      gaze.remove(file);
+    });
   };
 
-  var watch = [];
-  var graph = buildGraph(options);
-
-  // Add all files to watch list
-  for (var i in graph.index) {
-    watch.push(i);
-  }
+  watcher.reset(options);
 
   var gaze = new Gaze();
-  gaze.add(watch);
+  gaze.add(watcher.reset(options));
   gaze.on('error', emitter.emit.bind(emitter, 'error'));
 
   gaze.on('changed', function(file) {
-    var files = [file];
-
-    // descendents may be added, so we need a new graph
-    graph = buildGraph(options);
-    graph.visitAncestors(file, function(parent) {
-      files.push(parent);
-    });
-
-    // Add children to watcher
-    graph.visitDescendents(file, function(child) {
-      if (watch.indexOf(child) === -1) {
-        watch.push(child);
-        gaze.add(child);
-      }
-    });
-    files.forEach(function(file) {
-      if (path.basename(file)[0] !== '_') {
-        renderFile(file, options, emitter);
-      }
-    });
+    handler(watcher.changed(file));
   });
 
-  gaze.on('added', function() {
-    graph = buildGraph(options);
+  gaze.on('added', function(file) {
+    handler(watcher.added(file));
   });
 
-  gaze.on('deleted', function() {
-    graph = buildGraph(options);
+  gaze.on('deleted', function(file) {
+    handler(watcher.deleted(file));
   });
 }
 

lib/watcher.js

@@ -0,0 +1,84 @@
+var grapher = require('sass-graph'),
+  clonedeep = require('lodash.clonedeep'),
+  watcher = {
+    opts: {}
+  },
+  graph = null;
+
+watcher.reset = function(opts) {
+  this.opts = clonedeep(opts || this.opts || {});
+  var options = {
+    loadPaths: this.opts.includePath,
+    extensions: ['scss', 'sass', 'css']
+  };
+
+  if (this.opts.directory) {
+    graph = grapher.parseDir(this.opts.directory, options);
+  } else {
+    graph = grapher.parseFile(this.opts.src, options);
+  }
+
+  return Object.keys(graph.index);
+};
+
+watcher.changed = function(absolutePath) {
+  var files = {
+    added: [],
+    changed: [],
+    removed: [],
+  };
+
+  this.reset();
+
+  graph.visitAncestors(absolutePath, function(parent) {
+    files.changed.push(parent);
+  });
+
+  graph.visitDescendents(absolutePath, function(child) {
+    files.added.push(child);
+  });
+
+  return files;
+};
+
+watcher.added = function(absolutePath) {
+  var files = {
+    added: [],
+    changed: [],
+    removed: [],
+  };
+
+  this.reset();
+
+  if (Object.keys(graph.index).indexOf(absolutePath) !== -1) {
+    files.added.push(absolutePath);
+  }
+
+  graph.visitDescendents(absolutePath, function(child) {
+    files.added.push(child);
+  });
+
+  return files;
+};
+
+watcher.removed = function(absolutePath) {
+  var files = {
+    added: [],
+    changed: [],
+    removed: [],
+  };
+
+  graph.visitAncestors(absolutePath, function(parent) {
+    files.changed.push(parent);
+  });
+
+  if (Object.keys(graph.index).indexOf(absolutePath) !== -1) {
+    files.removed.push(absolutePath);
+  }
+
+  this.reset();
+
+  return files;
+};
+
+module.exports = watcher;

package.json

@@ -75,12 +75,14 @@
   "devDependencies": {
     "coveralls": "^2.11.8",
     "eslint": "^3.4.0",
+    "fs-extra": "^0.30.0",
     "istanbul": "^0.4.2",
     "mocha": "^3.1.2",
     "mocha-lcov-reporter": "^1.2.0",
     "object-merge": "^2.5.1",
     "read-yaml": "^1.0.0",
     "rimraf": "^2.5.2",
-    "sass-spec": "3.5.0-1"
+    "sass-spec": "3.5.0-1",
+    "unique-temp-dir": "^1.0.0"
   }
 }

test/fixtures/watcher/main/one.scss

@@ -0,0 +1,5 @@
+@import "partials/one";
+
+.one {
+  color: red;
+}

test/fixtures/watcher/main/partials/_one.scss

@@ -0,0 +1,3 @@
+.one {
+  color: darkred;
+}

test/fixtures/watcher/main/partials/_three.scss

@@ -0,0 +1,3 @@
+.three {
+  color: darkgreen;
+}

test/fixtures/watcher/main/partials/_two.scss

@@ -0,0 +1,3 @@
+.two {
+  color: darkblue;
+}

test/fixtures/watcher/main/two.scss

@@ -0,0 +1,5 @@
+@import "partials/two";
+
+.two {
+  color: blue;
+}

test/fixtures/watcher/sibling/partials/_three.scss

@@ -0,0 +1,3 @@
+.three {
+  color: darkgreen;
+}

test/fixtures/watcher/sibling/three.scss

@@ -0,0 +1,5 @@
+@import "partials/three";
+
+.three {
+  color: green;
+}