remark: Fix line highlighting

README.md

@@ -170,7 +170,7 @@ region name:
 To define the region in the referenced file put `#region some-region-name` and
 `#endregion some-region-name` as a comment line.
 
-Highlighting specific lines also work:
+Highlighting specific lines also work by passing them as a third parameter:
 
 ```markdown
 ![code go {4-6}](../../examples/somefile.go)

src/remark/code-block-snippets.test.ts

@@ -85,53 +85,19 @@ test('region', () => {
     expect(node.value.split("\n").length).toBe(4);
 });
 
-test('highlight-line-numbers', () => {
-    let node = {
-        type: 'paragraph',
-        children: [{
-            type: 'image',
-            alt: 'code {4-6}',
-            url: 'src/remark/code-block-snippets.test.ts',
-        }],
-    };
-
-    visitor(node);
-
-    expect(node.type).toBe('code');
-    expect(node.meta).toBe('{4-6}');
-});
-
-test('highlight-line-numbers-title', () => {
-    let node = {
-        type: 'paragraph',
-        children: [{
-            type: 'image',
-            alt: 'code {4-6}',
-            url: 'src/remark/code-block-snippets.test.ts',
-            title: 'Some title',
-        }],
-    };
-
-    visitor(node);
-
-    expect(node.type).toBe('code');
-    expect(node.meta).toBe('{4-6} title="Some title"');
-});
-
 test('highlight-line-numbers-lang', () => {
     let node = {
         type: 'paragraph',
         children: [{
             type: 'image',
-            alt: 'code text {4-6}',
+            alt: 'code text 4-6', // {4-6} curly brackets are automatically stripped.
             url: 'src/remark/code-block-snippets.test.ts',
         }],
     };
 
     visitor(node);
 
     expect(node.type).toBe('code');
-    expect(node.lang).toBe('text');
     expect(node.meta).toBe('{4-6}');
 });
 
@@ -140,7 +106,7 @@ test('highlight-line-numbers-lang-title', () => {
         type: 'paragraph',
         children: [{
             type: 'image',
-            alt: 'code text {4-6}',
+            alt: 'code text 4-6', // {4-6} curly brackets are automatically stripped.
             url: 'src/remark/code-block-snippets.test.ts',
             title: 'Some title',
         }],

src/remark/code-block-snippets.ts

@@ -56,10 +56,10 @@ export function visitor(untypedNode: mdast.Node): asserts untypedNode is mdast.C
         node.meta = `title="${imgNode.title}"`;
     }
 
-    // Highlight line numbers, if {some-range,and,some,more,lines} syntax used.
-    const lineNumber = imgNode.alt.match(/(\{.*\})/g);
+    // Highlight line numbers, if the third argument is passed. The curly brackets are already stripped. e.g. some-range,and,some,more,lines
+    const lineNumber = imgNode.alt.split(" ")[2];
     if (lineNumber) {
-        node.meta = lineNumber[0] + (node.meta?" "+node.meta:"");
+        node.meta = `{${lineNumber}}${node.meta?" "+node.meta:""}`;
     }
 
     // Source filename can have fragment symbol # followed by the line number(s) or region name.