LibMarkdown: Implement "tightness" for lists

From the commonmark spec:
A list is loose if any of its constituent list items are separated by
blank lines, or if any of its constituent list items directly contain
two block-level elements with a blank line between them. Otherwise a
list is tight. (The difference in HTML output is that paragraphs in a
loose list are wrapped in <p> tags, while paragraphs in a tight list are
not.)

15 files changed, 75 insertions, 28 deletions

diff --git a/Userland/Libraries/LibMarkdown/Block.h b/Userland/Libraries/LibMarkdown/Block.h
index 7e5fb393d5..bc5ec0e897 100644
--- a/Userland/Libraries/LibMarkdown/Block.h
+++ b/Userland/Libraries/LibMarkdown/Block.h
@@ -15,7 +15,7 @@ class Block {
 public:
     virtual ~Block() { }
 
-    virtual String render_to_html() const = 0;
+    virtual String render_to_html(bool tight = false) const = 0;
     virtual String render_for_terminal(size_t view_width = 0) const = 0;
 };
 
diff --git a/Userland/Libraries/LibMarkdown/CodeBlock.cpp b/Userland/Libraries/LibMarkdown/CodeBlock.cpp
index e3e946dba0..d433d3c61e 100644
--- a/Userland/Libraries/LibMarkdown/CodeBlock.cpp
+++ b/Userland/Libraries/LibMarkdown/CodeBlock.cpp
@@ -11,7 +11,7 @@
 
 namespace Markdown {
 
-String CodeBlock::render_to_html() const
+String CodeBlock::render_to_html(bool) const
 {
     StringBuilder builder;
 
diff --git a/Userland/Libraries/LibMarkdown/CodeBlock.h b/Userland/Libraries/LibMarkdown/CodeBlock.h
index 7b353956d2..c4b7ff7885 100644
--- a/Userland/Libraries/LibMarkdown/CodeBlock.h
+++ b/Userland/Libraries/LibMarkdown/CodeBlock.h
@@ -23,7 +23,7 @@ public:
     }
     virtual ~CodeBlock() override { }
 
-    virtual String render_to_html() const override;
+    virtual String render_to_html(bool tight = false) const override;
     virtual String render_for_terminal(size_t view_width = 0) const override;
     static OwnPtr<CodeBlock> parse(LineIterator& lines);
 
diff --git a/Userland/Libraries/LibMarkdown/ContainerBlock.cpp b/Userland/Libraries/LibMarkdown/ContainerBlock.cpp
index 7585d635ee..9585264661 100644
--- a/Userland/Libraries/LibMarkdown/ContainerBlock.cpp
+++ b/Userland/Libraries/LibMarkdown/ContainerBlock.cpp
@@ -14,15 +14,26 @@
 
 namespace Markdown {
 
-String ContainerBlock::render_to_html() const
+String ContainerBlock::render_to_html(bool tight) const
 {
     StringBuilder builder;
 
-    for (auto& block : m_blocks) {
-        auto s = block.render_to_html();
+    for (size_t i = 0; i + 1 < m_blocks.size(); ++i) {
+        auto s = m_blocks[i].render_to_html(tight);
         builder.append(s);
     }
 
+    // I don't like this edge case.
+    if (m_blocks.size() != 0) {
+        auto& block = m_blocks[m_blocks.size() - 1];
+        auto s = block.render_to_html(tight);
+        if (tight && dynamic_cast<Paragraph const*>(&block)) {
+            builder.append(s.substring_view(0, s.length() - 1));
+        } else {
+            builder.append(s);
+        }
+    }
+
     return builder.build();
 }
 
@@ -62,15 +73,21 @@ OwnPtr<ContainerBlock> ContainerBlock::parse(LineIterator& lines)
         paragraph_text.clear();
     };
 
+    bool has_blank_lines = false;
+    bool has_trailing_blank_lines = false;
+
     while (true) {
         if (lines.is_end())
             break;
 
         if ((*lines).is_empty()) {
+            has_trailing_blank_lines = true;
             ++lines;
 
             flush_paragraph();
             continue;
+        } else {
+            has_blank_lines = has_blank_lines || has_trailing_blank_lines;
         }
 
         bool any = try_parse_block<Table>(lines, blocks) || try_parse_block<List>(lines, blocks) || try_parse_block<CodeBlock>(lines, blocks)
@@ -92,7 +109,7 @@ OwnPtr<ContainerBlock> ContainerBlock::parse(LineIterator& lines)
 
     flush_paragraph();
 
-    return make<ContainerBlock>(move(blocks));
+    return make<ContainerBlock>(move(blocks), has_blank_lines, has_trailing_blank_lines);
 }
 
 }
diff --git a/Userland/Libraries/LibMarkdown/ContainerBlock.h b/Userland/Libraries/LibMarkdown/ContainerBlock.h
index 682f850c69..c737a6fc0e 100644
--- a/Userland/Libraries/LibMarkdown/ContainerBlock.h
+++ b/Userland/Libraries/LibMarkdown/ContainerBlock.h
@@ -16,20 +16,29 @@ namespace Markdown {
 
 class ContainerBlock final : public Block {
 public:
-    ContainerBlock(NonnullOwnPtrVector<Block> blocks)
+    ContainerBlock(NonnullOwnPtrVector<Block> blocks, bool has_blank_lines, bool has_trailing_blank_lines)
         : m_blocks(move(blocks))
+        , m_has_blank_lines(has_blank_lines)
+        , m_has_trailing_blank_lines(has_trailing_blank_lines)
     {
     }
 
     virtual ~ContainerBlock() override { }
 
-    virtual String render_to_html() const override;
+    virtual String render_to_html(bool tight = false) const override;
     virtual String render_for_terminal(size_t view_width = 0) const override;
 
     static OwnPtr<ContainerBlock> parse(LineIterator& lines);
 
+    bool has_blank_lines() const { return m_has_blank_lines; }
+    bool has_trailing_blank_lines() const { return m_has_trailing_blank_lines; }
+
+    NonnullOwnPtrVector<Block> const& blocks() const { return m_blocks; }
+
 private:
     NonnullOwnPtrVector<Block> m_blocks;
+    bool m_has_blank_lines;
+    bool m_has_trailing_blank_lines;
 };
 
 }
diff --git a/Userland/Libraries/LibMarkdown/Heading.cpp b/Userland/Libraries/LibMarkdown/Heading.cpp
index 50fe6219f9..66c8d4b02d 100644
--- a/Userland/Libraries/LibMarkdown/Heading.cpp
+++ b/Userland/Libraries/LibMarkdown/Heading.cpp
@@ -9,7 +9,7 @@
 
 namespace Markdown {
 
-String Heading::render_to_html() const
+String Heading::render_to_html(bool) const
 {
     return String::formatted("<h{}>{}</h{}>\n", m_level, m_text.render_to_html(), m_level);
 }
diff --git a/Userland/Libraries/LibMarkdown/Heading.h b/Userland/Libraries/LibMarkdown/Heading.h
index 6378636475..4e7ffa1948 100644
--- a/Userland/Libraries/LibMarkdown/Heading.h
+++ b/Userland/Libraries/LibMarkdown/Heading.h
@@ -25,7 +25,7 @@ public:
     }
     virtual ~Heading() override { }
 
-    virtual String render_to_html() const override;
+    virtual String render_to_html(bool tight = false) const override;
     virtual String render_for_terminal(size_t view_width = 0) const override;
     static OwnPtr<Heading> parse(LineIterator& lines);
 
diff --git a/Userland/Libraries/LibMarkdown/HorizontalRule.cpp b/Userland/Libraries/LibMarkdown/HorizontalRule.cpp
index 4f20d186ea..5d884df3db 100644
--- a/Userland/Libraries/LibMarkdown/HorizontalRule.cpp
+++ b/Userland/Libraries/LibMarkdown/HorizontalRule.cpp
@@ -10,7 +10,7 @@
 
 namespace Markdown {
 
-String HorizontalRule::render_to_html() const
+String HorizontalRule::render_to_html(bool) const
 {
     return "<hr />\n";
 }
diff --git a/Userland/Libraries/LibMarkdown/HorizontalRule.h b/Userland/Libraries/LibMarkdown/HorizontalRule.h
index f4568ce214..034b2233ea 100644
--- a/Userland/Libraries/LibMarkdown/HorizontalRule.h
+++ b/Userland/Libraries/LibMarkdown/HorizontalRule.h
@@ -21,7 +21,7 @@ public:
     }
     virtual ~HorizontalRule() override { }
 
-    virtual String render_to_html() const override;
+    virtual String render_to_html(bool tight = false) const override;
     virtual String render_for_terminal(size_t view_width = 0) const override;
     static OwnPtr<HorizontalRule> parse(LineIterator& lines);
 };
diff --git a/Userland/Libraries/LibMarkdown/List.cpp b/Userland/Libraries/LibMarkdown/List.cpp
index 393ff2899c..a75757b6e9 100644
--- a/Userland/Libraries/LibMarkdown/List.cpp
+++ b/Userland/Libraries/LibMarkdown/List.cpp
@@ -7,10 +7,11 @@
 
 #include <AK/StringBuilder.h>
 #include <LibMarkdown/List.h>
+#include <LibMarkdown/Paragraph.h>
 
 namespace Markdown {
 
-String List::render_to_html() const
+String List::render_to_html(bool) const
 {
     StringBuilder builder;
 
@@ -18,8 +19,10 @@ String List::render_to_html() const
     builder.appendff("<{}>\n", tag);
 
     for (auto& item : m_items) {
-        builder.append("<li>\n");
-        builder.append(item->render_to_html());
+        builder.append("<li>");
+        if (!m_is_tight || (item->blocks().size() != 0 && !dynamic_cast<Paragraph const*>(&(item->blocks()[0]))))
+            builder.append("\n");
+        builder.append(item->render_to_html(m_is_tight));
         builder.append("</li>\n");
     }
 
@@ -53,12 +56,15 @@ OwnPtr<List> List::parse(LineIterator& lines)
 
     bool first = true;
     bool is_ordered = false;
+
+    bool is_tight = true;
+    bool has_trailing_blank_lines = false;
+
     while (!lines.is_end()) {
+
         size_t offset = 0;
 
         const StringView& line = *lines;
-        if (line.is_empty())
-            break;
 
         bool appears_unordered = false;
         if (line.length() > 2) {
@@ -98,18 +104,23 @@ OwnPtr<List> List::parse(LineIterator& lines)
             break;
         }
 
+        is_tight = is_tight && !has_trailing_blank_lines;
+
         size_t saved_indent = lines.indent();
         lines.set_indent(saved_indent + offset);
         lines.ignore_next_prefix();
 
-        items.append(ContainerBlock::parse(lines));
+        auto list_item = ContainerBlock::parse(lines);
+        is_tight = is_tight && !list_item->has_blank_lines();
+        has_trailing_blank_lines = has_trailing_blank_lines || list_item->has_trailing_blank_lines();
+        items.append(move(list_item));
 
         lines.set_indent(saved_indent);
 
         first = false;
     }
 
-    return make<List>(move(items), is_ordered);
+    return make<List>(move(items), is_ordered, is_tight);
 }
 
 }
diff --git a/Userland/Libraries/LibMarkdown/List.h b/Userland/Libraries/LibMarkdown/List.h
index ee484c50e8..90492f6654 100644
--- a/Userland/Libraries/LibMarkdown/List.h
+++ b/Userland/Libraries/LibMarkdown/List.h
@@ -15,14 +15,15 @@ namespace Markdown {
 
 class List final : public Block {
 public:
-    List(Vector<OwnPtr<ContainerBlock>> items, bool is_ordered)
+    List(Vector<OwnPtr<ContainerBlock>> items, bool is_ordered, bool is_tight)
         : m_items(move(items))
         , m_is_ordered(is_ordered)
+        , m_is_tight(is_tight)
     {
     }
     virtual ~List() override { }
 
-    virtual String render_to_html() const override;
+    virtual String render_to_html(bool tight = false) const override;
     virtual String render_for_terminal(size_t view_width = 0) const override;
 
     static OwnPtr<List> parse(LineIterator& lines);
@@ -30,6 +31,7 @@ public:
 private:
     Vector<OwnPtr<ContainerBlock>> m_items;
     bool m_is_ordered { false };
+    bool m_is_tight { false };
 };
 
 }
diff --git a/Userland/Libraries/LibMarkdown/Paragraph.cpp b/Userland/Libraries/LibMarkdown/Paragraph.cpp
index c2c1111266..df0e3f2aea 100644
--- a/Userland/Libraries/LibMarkdown/Paragraph.cpp
+++ b/Userland/Libraries/LibMarkdown/Paragraph.cpp
@@ -9,12 +9,20 @@
 
 namespace Markdown {
 
-String Paragraph::render_to_html() const
+String Paragraph::render_to_html(bool tight) const
 {
     StringBuilder builder;
-    builder.append("<p>");
+
+    if (!tight)
+        builder.append("<p>");
+
     builder.append(m_text.render_to_html());
-    builder.append("</p>\n");
+
+    if (!tight)
+        builder.append("</p>");
+
+    builder.append('\n');
+
     return builder.build();
 }
 
diff --git a/Userland/Libraries/LibMarkdown/Paragraph.h b/Userland/Libraries/LibMarkdown/Paragraph.h
index 4b75e1cd67..e9c8db692e 100644
--- a/Userland/Libraries/LibMarkdown/Paragraph.h
+++ b/Userland/Libraries/LibMarkdown/Paragraph.h
@@ -22,7 +22,7 @@ public:
 
     virtual ~Paragraph() override { }
 
-    virtual String render_to_html() const override;
+    virtual String render_to_html(bool tight = false) const override;
     virtual String render_for_terminal(size_t view_width = 0) const override;
 
 private:
diff --git a/Userland/Libraries/LibMarkdown/Table.cpp b/Userland/Libraries/LibMarkdown/Table.cpp
index 692e2877bb..37f3c1ad5a 100644
--- a/Userland/Libraries/LibMarkdown/Table.cpp
+++ b/Userland/Libraries/LibMarkdown/Table.cpp
@@ -65,7 +65,7 @@ String Table::render_for_terminal(size_t view_width) const
     return builder.to_string();
 }
 
-String Table::render_to_html() const
+String Table::render_to_html(bool) const
 {
     StringBuilder builder;
 
diff --git a/Userland/Libraries/LibMarkdown/Table.h b/Userland/Libraries/LibMarkdown/Table.h
index 76e0143c21..a4f4d0e578 100644
--- a/Userland/Libraries/LibMarkdown/Table.h
+++ b/Userland/Libraries/LibMarkdown/Table.h
@@ -32,7 +32,7 @@ public:
     Table() { }
     virtual ~Table() override { }
 
-    virtual String render_to_html() const override;
+    virtual String render_to_html(bool tight = false) const override;
     virtual String render_for_terminal(size_t view_width = 0) const override;
     static OwnPtr<Table> parse(LineIterator& lines);