fix: issue #6813 (Zero-based lists are broken) (#6852)

changelog_unreleased/markdown/pr-6852.md

@@ -0,0 +1,19 @@
+#### Handle zero-based lists correctly ([#6852](https://github.com/prettier/prettier/pull/6852) by [@evilebottnawi](https://github.com/evilebottnawi))
+
+<!-- prettier-ignore -->
+```md
+<!-- Input -->
+0. List
+1. List
+2. List
+
+<!-- Prettier stable -->
+0. List
+1. List
+1. List
+
+<!-- Prettier master -->
+0. List
+1. List
+2. List
+```

src/language-markdown/printer-markdown.js

@@ -25,7 +25,7 @@ const {
 } = require("../doc");
 const {
   getFencedCodeBlockValue,
-  getOrderedListItemInfo,
+  hasGitDiffFriendlyOrderedList,
   splitText,
   punctuationPattern,
   INLINE_NODE_TYPES,
@@ -251,11 +251,10 @@ function genericPrint(path, options, print) {
         path.getParentNode()
       );
 
-      const isGitDiffFriendlyOrderedList =
-        node.ordered &&
-        node.children.length > 1 &&
-        +getOrderedListItemInfo(node.children[1], options.originalText)
-          .numberText === 1;
+      const isGitDiffFriendlyOrderedList = hasGitDiffFriendlyOrderedList(
+        node,
+        options
+      );
 
       return printChildren(path, options, print, {
         processor: (childPath, index) => {

src/language-markdown/utils.js

@@ -162,6 +162,34 @@ function getOrderedListItemInfo(orderListItem, originalText) {
   return { numberText, marker, leadingSpaces };
 }
 
+function hasGitDiffFriendlyOrderedList(node, options) {
+  if (!node.ordered) {
+    return false;
+  }
+
+  if (node.children.length < 2) {
+    return false;
+  }
+
+  const firstNumber = Number(
+    getOrderedListItemInfo(node.children[0], options.originalText).numberText
+  );
+
+  const secondNumber = Number(
+    getOrderedListItemInfo(node.children[1], options.originalText).numberText
+  );
+
+  if (firstNumber === 0 && node.children.length > 2) {
+    const thirdNumber = Number(
+      getOrderedListItemInfo(node.children[2], options.originalText).numberText
+    );
+
+    return secondNumber === 1 && thirdNumber === 1;
+  }
+
+  return secondNumber === 1;
+}
+
 // workaround for https://github.com/remarkjs/remark/issues/351
 // leading and trailing newlines are stripped by remark
 function getFencedCodeBlockValue(node, originalText) {
@@ -229,6 +257,7 @@ module.exports = {
   punctuationPattern,
   getFencedCodeBlockValue,
   getOrderedListItemInfo,
+  hasGitDiffFriendlyOrderedList,
   INLINE_NODE_TYPES,
   INLINE_NODE_WRAPPER_TYPES
 };

tests/markdown_list/__snapshots__/jsfmt.spec.js.snap

@@ -2458,11 +2458,200 @@ proseWrap: "always"
 6. def
 7. ghi
 
+---
+
+0. abc
+0. def
+0. ghi
+
+---
+
+1. abc
+1. def
+1. ghi
+
+---
+
+2. abc
+2. def
+2. ghi
+
+---
+
+0. abc
+1. def
+2. ghi
+
+---
+
+0. abc
+1. def
+1. ghi
+
+---
+
+1. abc
+2. def
+3. ghi
+
+---
+
+2. abc
+3. def
+4. ghi
+
+---
+
+999. abc
+145. def
+69. ghi
+
+---
+
+0. abc
+
+---
+
+1. abc
+
+---
+
+2. abc
+
+---
+
+999. abc
+
+---
+
+0. abc
+1. def
+
+---
+
+1. abc
+2. def
+
+---
+
+
+1. abc
+1. def
+
+---
+
+2. abc
+3. def
+
+---
+
+999. abc
+1. def
+
+---
+
+999. abc
+2. def
+
 =====================================output=====================================
 5. abc
 6. def
 7. ghi
 
+---
+
+0. abc
+1. def
+2. ghi
+
+---
+
+1. abc
+1. def
+1. ghi
+
+---
+
+2. abc
+3. def
+4. ghi
+
+---
+
+0. abc
+1. def
+2. ghi
+
+---
+
+0. abc
+1. def
+1. ghi
+
+---
+
+1. abc
+2. def
+3. ghi
+
+---
+
+2. abc
+3. def
+4. ghi
+
+---
+
+999. abc
+1000. def
+1001. ghi
+
+---
+
+0. abc
+
+---
+
+1. abc
+
+---
+
+2. abc
+
+---
+
+999. abc
+
+---
+
+0. abc
+1. def
+
+---
+
+1. abc
+2. def
+
+---
+
+1. abc
+1. def
+
+---
+
+2. abc
+3. def
+
+---
+
+999. abc
+1. def
+
+---
+
+999. abc
+1000. def
+
 ================================================================================
 `;
 
@@ -2478,11 +2667,200 @@ tabWidth: 4
 6. def
 7. ghi
 
+---
+
+0. abc
+0. def
+0. ghi
+
+---
+
+1. abc
+1. def
+1. ghi
+
+---
+
+2. abc
+2. def
+2. ghi
+
+---
+
+0. abc
+1. def
+2. ghi
+
+---
+
+0. abc
+1. def
+1. ghi
+
+---
+
+1. abc
+2. def
+3. ghi
+
+---
+
+2. abc
+3. def
+4. ghi
+
+---
+
+999. abc
+145. def
+69. ghi
+
+---
+
+0. abc
+
+---
+
+1. abc
+
+---
+
+2. abc
+
+---
+
+999. abc
+
+---
+
+0. abc
+1. def
+
+---
+
+1. abc
+2. def
+
+---
+
+
+1. abc
+1. def
+
+---
+
+2. abc
+3. def
+
+---
+
+999. abc
+1. def
+
+---
+
+999. abc
+2. def
+
 =====================================output=====================================
 5. abc
 6. def
 7. ghi
 
+---
+
+0. abc
+1. def
+2. ghi
+
+---
+
+1. abc
+1. def
+1. ghi
+
+---
+
+2. abc
+3. def
+4. ghi
+
+---
+
+0. abc
+1. def
+2. ghi
+
+---
+
+0. abc
+1. def
+1. ghi
+
+---
+
+1. abc
+2. def
+3. ghi
+
+---
+
+2. abc
+3. def
+4. ghi
+
+---
+
+999. abc
+1000. def
+1001. ghi
+
+---
+
+0. abc
+
+---
+
+1. abc
+
+---
+
+2. abc
+
+---
+
+999. abc
+
+---
+
+0. abc
+1. def
+
+---
+
+1. abc
+2. def
+
+---
+
+1. abc
+1. def
+
+---
+
+2. abc
+3. def
+
+---
+
+999. abc
+1. def
+
+---
+
+999. abc
+1000. def
+
 ================================================================================
 `;
 
@@ -2498,11 +2876,200 @@ tabWidth: 999
 6. def
 7. ghi
 
+---
+
+0. abc
+0. def
+0. ghi
+
+---
+
+1. abc
+1. def
+1. ghi
+
+---
+
+2. abc
+2. def
+2. ghi
+
+---
+
+0. abc
+1. def
+2. ghi
+
+---
+
+0. abc
+1. def
+1. ghi
+
+---
+
+1. abc
+2. def
+3. ghi
+
+---
+
+2. abc
+3. def
+4. ghi
+
+---
+
+999. abc
+145. def
+69. ghi
+
+---
+
+0. abc
+
+---
+
+1. abc
+
+---
+
+2. abc
+
+---
+
+999. abc
+
+---
+
+0. abc
+1. def
+
+---
+
+1. abc
+2. def
+
+---
+
+
+1. abc
+1. def
+
+---
+
+2. abc
+3. def
+
+---
+
+999. abc
+1. def
+
+---
+
+999. abc
+2. def
+
 =====================================output=====================================
 5. abc
 6. def
 7. ghi
 
+---
+
+0. abc
+1. def
+2. ghi
+
+---
+
+1. abc
+1. def
+1. ghi
+
+---
+
+2. abc
+3. def
+4. ghi
+
+---
+
+0. abc
+1. def
+2. ghi
+
+---
+
+0. abc
+1. def
+1. ghi
+
+---
+
+1. abc
+2. def
+3. ghi
+
+---
+
+2. abc
+3. def
+4. ghi
+
+---
+
+999. abc
+1000. def
+1001. ghi
+
+---
+
+0. abc
+
+---
+
+1. abc
+
+---
+
+2. abc
+
+---
+
+999. abc
+
+---
+
+0. abc
+1. def
+
+---
+
+1. abc
+2. def
+
+---
+
+1. abc
+1. def
+
+---
+
+2. abc
+3. def
+
+---
+
+999. abc
+1. def
+
+---
+
+999. abc
+1000. def
+
 ================================================================================
 `;
 
@@ -2518,10 +3085,199 @@ tabWidth: 0
 6. def
 7. ghi
 
+---
+
+0. abc
+0. def
+0. ghi
+
+---
+
+1. abc
+1. def
+1. ghi
+
+---
+
+2. abc
+2. def
+2. ghi
+
+---
+
+0. abc
+1. def
+2. ghi
+
+---
+
+0. abc
+1. def
+1. ghi
+
+---
+
+1. abc
+2. def
+3. ghi
+
+---
+
+2. abc
+3. def
+4. ghi
+
+---
+
+999. abc
+145. def
+69. ghi
+
+---
+
+0. abc
+
+---
+
+1. abc
+
+---
+
+2. abc
+
+---
+
+999. abc
+
+---
+
+0. abc
+1. def
+
+---
+
+1. abc
+2. def
+
+---
+
+
+1. abc
+1. def
+
+---
+
+2. abc
+3. def
+
+---
+
+999. abc
+1. def
+
+---
+
+999. abc
+2. def
+
 =====================================output=====================================
 5. abc
 6. def
 7. ghi
 
+---
+
+0. abc
+1. def
+2. ghi
+
+---
+
+1. abc
+1. def
+1. ghi
+
+---
+
+2. abc
+3. def
+4. ghi
+
+---
+
+0. abc
+1. def
+2. ghi
+
+---
+
+0. abc
+1. def
+1. ghi
+
+---
+
+1. abc
+2. def
+3. ghi
+
+---
+
+2. abc
+3. def
+4. ghi
+
+---
+
+999. abc
+1000. def
+1001. ghi
+
+---
+
+0. abc
+
+---
+
+1. abc
+
+---
+
+2. abc
+
+---
+
+999. abc
+
+---
+
+0. abc
+1. def
+
+---
+
+1. abc
+2. def
+
+---
+
+1. abc
+1. def
+
+---
+
+2. abc
+3. def
+
+---
+
+999. abc
+1. def
+
+---
+
+999. abc
+1000. def
+
 ================================================================================
 `;

tests/markdown_list/start.md

@@ -1,3 +1,98 @@
 5. abc
 6. def
 7. ghi
+
+---
+
+0. abc
+0. def
+0. ghi
+
+---
+
+1. abc
+1. def
+1. ghi
+
+---
+
+2. abc
+2. def
+2. ghi
+
+---
+
+0. abc
+1. def
+2. ghi
+
+---
+
+0. abc
+1. def
+1. ghi
+
+---
+
+1. abc
+2. def
+3. ghi
+
+---
+
+2. abc
+3. def
+4. ghi
+
+---
+
+999. abc
+145. def
+69. ghi
+
+---
+
+0. abc
+
+---
+
+1. abc
+
+---
+
+2. abc
+
+---
+
+999. abc
+
+---
+
+0. abc
+1. def
+
+---
+
+1. abc
+2. def
+
+---
+
+
+1. abc
+1. def
+
+---
+
+2. abc
+3. def
+
+---
+
+999. abc
+1. def
+
+---
+
+999. abc
+2. def