[clangd] Separate chunks with a space when rendering markdown

[ilya-biryukov]

Summary

This results in better rendering of resulting markdown.

Especially noticeable in coc.nvim that does not have a visible horizontal
spaces around inline code blocks. More details and a screenshot from
coc.nvim can be found in https://github.com/clangd/clangd/issues/95.

clang-tools-extra/trunk/clangd/FormattedString.cpp

void FormattedString::appendInlineCode(std::string Code) {
   Chunk C;
   C.Kind = ChunkKind::InlineCodeBlock;
   C.Contents = std::move(Code);
   Chunks.push_back(std::move(C));
 }
 
 std::string FormattedString::renderAsMarkdown() const {
   std::string R;
+  auto EnsureWhitespace = [&R]() {
+    // Adds a space for nicer rendering.
+    if (!R.empty() && !isWhitespace(R.back()))
+      R += " ";
+  };
   for (const auto &C : Chunks) {
     switch (C.Kind) {
     case ChunkKind::PlainText:
+      if (!C.Contents.empty() && !isWhitespace(C.Contents.front()))
+        EnsureWhitespace();
       R += renderText(C.Contents);
       continue;
     case ChunkKind::InlineCodeBlock:
-      // Make sure we don't glue two backticks together.
-      if (llvm::StringRef(R).endswith("`"))
-        R += " ";
+      EnsureWhitespace();
       R += renderInlineBlock(C.Contents);
       continue;
     case ChunkKind::CodeBlock:
       if (!R.empty() && !llvm::StringRef(R).endswith("\n"))
         R += "\n";
       R += renderCodeBlock(C.Contents, C.Language);
       R += "\n";
       continue;

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

after)md";
   EXPECT_EQ(S.renderAsMarkdown(), "`foobar` `bazqux`");
 
   S = FormattedString();
   S.appendText("foo");
   S.appendInlineCode("bar");
   S.appendText("baz");
 
   EXPECT_EQ(S.renderAsPlainText(), "foo bar baz");
-  EXPECT_EQ(S.renderAsMarkdown(), "foo`bar`baz");
+  EXPECT_EQ(S.renderAsMarkdown(), "foo `bar` baz");
 }
 
 TEST(FormattedString, Escaping) {
   // Check some ASCII punctuation
   FormattedString S;
   S.appendText("*!`");
   EXPECT_EQ(S.renderAsMarkdown(), "\\*\\!\\`");
 
EXPECT_EQ(S.renderAsMarkdown(), "````cpp\n"
                                   "````\n");
   S = FormattedString();
   S.appendCodeBlock("foobarbaz ` `` ``` ```` `\nqux");
   EXPECT_EQ(S.renderAsMarkdown(), "`````cpp\n"
                                   "foobarbaz ` `` ``` ```` `\nqux\n"
                                   "`````\n");
 }
 
+TEST(FormattedString, MarkdownWhitespace) {
+  // Whitespace should be added as separators between blocks.
+  FormattedString S;
+  S.appendText("foo");
+  S.appendText("bar");
+  EXPECT_EQ(S.renderAsMarkdown(), "foo bar");
+
+  S = FormattedString();
+  S.appendInlineCode("foo");
+  S.appendInlineCode("bar");
+  EXPECT_EQ(S.renderAsMarkdown(), "`foo` `bar`");
+
+  // However, we don't want to add any extra whitespace.
+  S = FormattedString();
+  S.appendText("foo ");
+  S.appendInlineCode("bar");
+  EXPECT_EQ(S.renderAsMarkdown(), "foo `bar`");
+
+  S = FormattedString();
+  S.appendText("foo\n");
+  S.appendInlineCode("bar");
+  EXPECT_EQ(S.renderAsMarkdown(), "foo\n`bar`");
+
+  S = FormattedString();
+  S.appendInlineCode("foo");
+  S.appendText(" bar");
+  EXPECT_EQ(S.renderAsMarkdown(), "`foo` bar");
+
+  S = FormattedString();
+  S.appendText("foo");
+  S.appendCodeBlock("bar");
+  S.appendText("baz");
+  EXPECT_EQ(S.renderAsMarkdown(), "foo\n```cpp\nbar\n```\nbaz");
+}
+
+
 } // namespace
 } // namespace clangd
 } // namespace clang