Update to match quirks of unified diff format (#297)

src/patch/create.js

@@ -72,8 +72,9 @@ export function structuredPatch(oldFileName, newFileName, oldStr, newStr, oldHea
             let oldEOFNewline = ((/\n$/).test(oldStr));
             let newEOFNewline = ((/\n$/).test(newStr));
             let noNlBeforeAdds = lines.length == 0 && curRange.length > hunk.oldLines;
-            if (!oldEOFNewline && noNlBeforeAdds) {
+            if (!oldEOFNewline && noNlBeforeAdds && oldStr.length > 0) {
               // special case: old has no eol and no trailing context; no-nl can end up before adds
+              // however, if the old file is empty, do not output the no-nl line
               curRange.splice(hunk.oldLines, 0, '\\ No newline at end of file');
             }
             if ((!oldEOFNewline && !noNlBeforeAdds) || !newEOFNewline) {
@@ -110,6 +111,15 @@ export function formatPatch(diff) {
 
   for (let i = 0; i < diff.hunks.length; i++) {
     const hunk = diff.hunks[i];
+    // Unified Diff Format quirk: If the chunk size is 0,
+    // the first number is one lower than one would expect.
+    // https://www.artima.com/weblogs/viewpost.jsp?thread=164293
+    if (hunk.oldLines === 0) {
+      hunk.oldStart -= 1;
+    }
+    if (hunk.newLines === 0) {
+      hunk.newStart -= 1;
+    }
     ret.push(
       '@@ -' + hunk.oldStart + ',' + hunk.oldLines
       + ' +' + hunk.newStart + ',' + hunk.newLines

src/patch/parse.js

@@ -77,13 +77,23 @@ export function parsePatch(uniDiff, options = {}) {
 
     let hunk = {
       oldStart: +chunkHeader[1],
-      oldLines: +chunkHeader[2] || 1,
+      oldLines: typeof chunkHeader[2] === 'undefined' ? 1 : +chunkHeader[2],
       newStart: +chunkHeader[3],
-      newLines: +chunkHeader[4] || 1,
+      newLines: typeof chunkHeader[4] === 'undefined' ? 1 : +chunkHeader[4],
       lines: [],
       linedelimiters: []
     };
 
+    // Unified Diff Format quirk: If the chunk size is 0,
+    // the first number is one lower than one would expect.
+    // https://www.artima.com/weblogs/viewpost.jsp?thread=164293
+    if (hunk.oldLines === 0) {
+      hunk.oldStart += 1;
+    }
+    if (hunk.newLines === 0) {
+      hunk.newStart += 1;
+    }
+
     let addCount = 0,
         removeCount = 0;
     for (; i < diffstr.length; i++) {

test/patch/apply.js

@@ -355,6 +355,160 @@ describe('patch/apply', function() {
           + 'line5\n');
     });
 
+    it('should apply single line patches with zero context and zero removed', function() {
+      expect(applyPatch(
+          'line2\n'
+          + 'line3\n'
+          + 'line5\n',
+
+          '--- test\theader1\n'
+          + '+++ test\theader2\n'
+          + '@@ -2,0 +3 @@\n'
+          + '+line4\n'))
+        .to.equal(
+          'line2\n'
+          + 'line3\n'
+          + 'line4\n'
+          + 'line5\n');
+    });
+
+    it('should apply multiline patches with zero context and zero removed', function() {
+      expect(applyPatch(
+          'line2\n'
+          + 'line3\n'
+          + 'line7\n',
+
+          '--- test\theader1\n'
+          + '+++ test\theader2\n'
+          + '@@ -2,0 +3,3 @@\n'
+          + '+line4\n'
+          + '+line5\n'
+          + '+line6\n'))
+        .to.equal(
+          'line2\n'
+          + 'line3\n'
+          + 'line4\n'
+          + 'line5\n'
+          + 'line6\n'
+          + 'line7\n');
+    });
+
+    it('should apply single line patches with zero context and zero removed at start of file', function() {
+      expect(applyPatch(
+          'line2\n'
+          + 'line3\n',
+
+          '--- test\theader1\n'
+          + '+++ test\theader2\n'
+          + '@@ -0,0 +1 @@\n'
+          + '+line1\n'))
+        .to.equal(
+          'line1\n'
+          + 'line2\n'
+          + 'line3\n');
+    });
+
+    it('should apply multi line patches with zero context and zero removed at start of file', function() {
+      expect(applyPatch(
+          'line3\n'
+          + 'line4\n',
+
+          '--- test\theader1\n'
+          + '+++ test\theader2\n'
+          + '@@ -0,0 +1,2 @@\n'
+          + '+line1\n'
+          + '+line2\n'))
+        .to.equal(
+          'line1\n'
+          + 'line2\n'
+          + 'line3\n'
+          + 'line4\n');
+    });
+
+    it('should apply multi line patches with zero context and zero removed at end of file', function() {
+      expect(applyPatch(
+          'line1\n',
+
+          '--- test\theader1\n'
+          + '+++ test\theader2\n'
+          + '@@ -1,0 +2 @@\n'
+          + '+line2\n'))
+        .to.equal(
+          'line1\n'
+          + 'line2\n');
+    });
+
+    it('should apply multi line patches with zero context and zero removed at end of file', function() {
+      expect(applyPatch(
+          'line1\n',
+
+          '--- test\theader1\n'
+          + '+++ test\theader2\n'
+          + '@@ -1,0 +2,2 @@\n'
+          + '+line2\n'
+          + '+line3\n'))
+        .to.equal(
+          'line1\n'
+          + 'line2\n'
+          + 'line3\n');
+    });
+
+    it('should apply single line patches with zero context and zero added at beginning of file', function() {
+      expect(applyPatch(
+          'line1\n'
+          + 'line2\n',
+
+          '--- test\theader1\n'
+          + '+++ test\theader2\n'
+          + '@@ -1 +0,0 @@\n'
+          + '-line1\n'))
+        .to.equal(
+          'line2\n');
+    });
+
+    it('should apply multi line patches with zero context and zero added at beginning of file', function() {
+      expect(applyPatch(
+          'line1\n'
+          + 'line2\n'
+          + 'line3\n',
+
+          '--- test\theader1\n'
+          + '+++ test\theader2\n'
+          + '@@ -1,2 +0,0 @@\n'
+          + '-line1\n'
+          + '-line2\n'))
+        .to.equal(
+          'line3\n');
+    });
+
+    it('should apply single line patches with zero context and zero added at end of file', function() {
+      expect(applyPatch(
+          'line1\n'
+          + 'line2\n',
+
+          '--- test\theader1\n'
+          + '+++ test\theader2\n'
+          + '@@ -2 +1,0 @@\n'
+          + '-line2\n'))
+        .to.equal(
+          'line1\n');
+    });
+
+    it('should apply multi line patches with zero context and zero added at end of file', function() {
+      expect(applyPatch(
+          'line1\n'
+          + 'line2\n'
+          + 'line3\n',
+
+          '--- test\theader1\n'
+          + '+++ test\theader2\n'
+          + '@@ -2,2 +1,0 @@\n'
+          + '-line2\n'
+          + '-line3\n'))
+        .to.equal(
+          'line1\n');
+    });
+
     it('should fail on mismatch', function() {
       expect(applyPatch(
           'line2\n'

test/patch/create.js

@@ -120,14 +120,13 @@ describe('patch/create', function() {
         + '\\ No newline at end of file\n');
     });
 
-    it('should output only one "no newline" at end of file message on empty file', function() {
+    it('should output no "no newline" at end of file message on empty file', function() {
       expect(createPatch('test', '', 'line1\nline2\nline3\nline4', 'header1', 'header2')).to.equal(
         'Index: test\n'
         + '===================================================================\n'
         + '--- test\theader1\n'
         + '+++ test\theader2\n'
-        + '@@ -1,0 +1,4 @@\n'
-        + '\\ No newline at end of file\n'
+        + '@@ -0,0 +1,4 @@\n'
         + '+line1\n'
         + '+line2\n'
         + '+line3\n'
@@ -139,7 +138,7 @@ describe('patch/create', function() {
         + '===================================================================\n'
         + '--- test\theader1\n'
         + '+++ test\theader2\n'
-        + '@@ -1,4 +1,0 @@\n'
+        + '@@ -1,4 +0,0 @@\n'
         + '-line1\n'
         + '-line2\n'
         + '-line3\n'
@@ -528,7 +527,7 @@ describe('patch/create', function() {
       expect(diffResult).to.equal(expectedResult);
     });
 
-    it('should generatea a patch with context size 0', function() {
+    it('should generate a patch with context size 0', function() {
       const expectedResult =
         'Index: testFileName\n'
         + '===================================================================\n'
@@ -538,11 +537,11 @@ describe('patch/create', function() {
         + '-value\n'
         + '+new value\n'
         + '+new value 2\n'
-        + '@@ -11,1 +12,0 @@\n'
+        + '@@ -11,1 +11,0 @@\n'
         + '-remove value\n'
-        + '@@ -21,1 +21,0 @@\n'
+        + '@@ -21,1 +20,0 @@\n'
         + '-remove value\n'
-        + '@@ -30,0 +29,1 @@\n'
+        + '@@ -29,0 +29,1 @@\n'
         + '+add value\n'
         + '@@ -34,1 +34,2 @@\n'
         + '-value\n'