Add NodeUtils.isBefore

lib/match.js

@@ -63,11 +63,9 @@ class Match {
     return nodeArrays.map((nodes) => {
       var filename = nodes[0].loc.filename;
 
-      var start = nodes.map(node => node.loc.start).reduce((res, curr) => {
-        var before = (curr.line === res.line && curr.column < res.column) ||
-          curr.line < res.line;
-        return before ? curr : res;
-      });
+      var start = nodes.reduce((res, curr) => {
+        return NodeUtils.isBefore(curr, res) ? curr : res;
+      }).loc.start;
 
       // The end line requires more careful approximation so as not to
       // accidentally include a large number of irrelevant src lines

lib/nodeUtils.js

@@ -1,3 +1,5 @@
+var stable = require('stable');
+
 /**
  * Cache for getChildren, holding the keys to traverse for a given Node type.
  */
@@ -109,6 +111,20 @@ class NodeUtils {
     return res;
   }
 
+  /**
+   * Returns whether or not the first node appears before the second, by
+   * comparing both their starting lines and columns.
+   *
+   * @param   {object} a
+   * @param   {object} b
+   * @returns {bool}
+   */
+  static isBefore(a, b) {
+    a = a.loc.start;
+    b = b.loc.start;
+    return a.line < b.line || (a.line === b.line && a.column < b.column);
+  }
+
   /**
    * Returns whether or not the nodes are part of an ES6 module import.
    *

spec/nodeUtilsSpec.js

@@ -78,6 +78,44 @@ describe('NodeUtils', function() {
     });
   });
 
+  describe('isBefore', function() {
+    describe('given nodes with different line numbers', function() {
+      it('returns true if the first node has a lower line number', function() {
+        var res = NodeUtils.isBefore(
+          {loc: {start: {line: 0, column: 0}}},
+          {loc: {start: {line: 1, column: 0}}}
+        );
+        expect(res).to.be(true);
+      });
+
+      it('returns false if the first node has a higher numbered line', function() {
+        var res = NodeUtils.isBefore(
+          {loc: {start: {line: 1, column: 0}}},
+          {loc: {start: {line: 0, column: 0}}}
+        );
+        expect(res).to.be(false);
+      });
+    });
+
+    describe('given nodes with the same line number', function() {
+      it('returns true if the first node has a lower column number', function() {
+        var res = NodeUtils.isBefore(
+          {loc: {start: {line: 0, column: 0}}},
+          {loc: {start: {line: 0, column: 1}}}
+        );
+        expect(res).to.be(true);
+      });
+
+      it('returns false if the first node has a higher column number', function() {
+        var res = NodeUtils.isBefore(
+          {loc: {start: {line: 0, column: 1}}},
+          {loc: {start: {line: 0, column: 0}}}
+        );
+        expect(res).to.be(false);
+      });
+    });
+  });
+
   describe('isES6ModuleImport', function() {
     it('returns true for an import declaration', function() {
       // ImportDeclaration