[clangd] Fix markdown rendering in VSCode

[kadircet]

Summary

Eventough it is OK to have a new line without any preceding spaces in
some markdown specifications, VSCode requires two spaces before a new line to
break a line inside a paragraph.

[merge_guards_bot]

Unit tests: pass. 61662 tests passed, 0 failed and 779 were skipped.

clang-tidy: pass.

clang-format: pass.

Build artifacts: diff.json, clang-tidy.txt, clang-format.patch, CMakeCache.txt, console-log.txt, test-results.xml

[ilya-biryukov]

LGTM

clang-tools-extra/clangd/FormattedString.cpp

for (auto &C : Chunks) {
     case Chunk::InlineCode:
       OS << renderInlineBlock(C.Contents);
       break;
     }
     Sep = " ";
   }
   // Paragraphs are translated into markdown lines, not markdown paragraphs.
   // Therefore it only has a single linebreak afterwards.
-  OS << '\n';
+  // VSCode requires two spaces at the end of line to start a new one.
+  OS << "  \n";
 }
 
 void Paragraph::renderPlainText(llvm::raw_ostream &OS) const {
   llvm::StringRef Sep = "";
   for (auto &C : Chunks) {
     OS << Sep << C.Contents;
     Sep = " ";
   }

clang-tools-extra/clangd/unittests/FormattedStringTests.cpp

 }
 
 TEST(Document, Separators) {
   Document D;
   D.addParagraph().appendText("foo");
   D.addCodeBlock("test");
   D.addParagraph().appendText("bar");
 
-  const char ExpectedMarkdown[] = R"md(foo
+  const char ExpectedMarkdown[] = R"md(foo  
 ```cpp
 test
 ```
 bar)md";
   EXPECT_EQ(D.asMarkdown(), ExpectedMarkdown);
 
   const char ExpectedText[] = R"pt(foo
 
 test
 
 bar)pt";
   EXPECT_EQ(D.asPlainText(), ExpectedText);
 }
 
 TEST(Document, Spacer) {
   Document D;
   D.addParagraph().appendText("foo");
   D.addSpacer();
   D.addParagraph().appendText("bar");
-  EXPECT_EQ(D.asMarkdown(), "foo\n\nbar");
+  EXPECT_EQ(D.asMarkdown(), "foo  \n\nbar");
   EXPECT_EQ(D.asPlainText(), "foo\n\nbar");
 }
 
 TEST(CodeBlock, Render) {
   Document D;
   // Code blocks preserves any extra spaces.
   D.addCodeBlock("foo\n  bar\n  baz");
 
- bar)pt");
   // Nest one more level.
   BulletList &InnerList = Inner.addBulletList();
   // Single item, baz\nbaz
   Document &DeepDoc = InnerList.addItem();
   DeepDoc.addParagraph().appendText("baz");
   DeepDoc.addParagraph().appendText("baz");
   EXPECT_EQ(L.asMarkdown(), R"md(- foo
 - bar
-- foo
-  baz
-  - foo
-    - baz
+- foo  
+  baz  
+  - foo  
+    - baz  
       baz)md");
   EXPECT_EQ(L.asPlainText(), R"pt(- foo
 - bar
 - foo
   baz
   - foo
     - baz
       baz)pt");
 
   // Termination
   Inner.addParagraph().appendText("after");
   EXPECT_EQ(L.asMarkdown(), R"md(- foo
 - bar
-- foo
-  baz
-  - foo
-    - baz
+- foo  
+  baz  
+  - foo  
+    - baz  
       baz
     
     after)md");
   EXPECT_EQ(L.asPlainText(), R"pt(- foo
 - bar
 - foo
   baz
   - foo