Shell: Do not treat the ending newline as part of a comment

This allows the parser to finally parse the entire source into a single
AST.
As a result of allowing comments inside sequences, Sequence is also
marked as would_execute if its left or right node would.

Shell/AST.cpp

@@ -556,7 +556,7 @@ void Comment::dump(int level) const
 
 RefPtr<Value> Comment::run(RefPtr<Shell>)
 {
-    return create<StringValue>("");
+    return create<ListValue>({});
 }
 
 void Comment::highlight_in_editor(Line::Editor& editor, Shell&, HighlightMetadata)
@@ -1229,7 +1229,27 @@ void Sequence::dump(int level) const
 
 RefPtr<Value> Sequence::run(RefPtr<Shell> shell)
 {
+    // If we are to return a job, block on the left one then return the right one.
+    if (would_execute()) {
+        RefPtr<AST::Node> execute_node = create<AST::Execute>(m_left->position(), m_left);
+        auto left_job = execute_node->run(shell);
+        ASSERT(left_job->is_job());
+        shell->block_on_job(static_cast<JobValue*>(left_job.ptr())->job());
+
+        if (m_right->would_execute())
+            return m_right->run(shell);
+
+        execute_node = create<AST::Execute>(m_right->position(), m_right);
+        return execute_node->run(shell);
+    }
     auto left = m_left->run(shell)->resolve_as_commands(shell);
+    // This could happen if a comment is next to a command.
+    if (left.size() == 1) {
+        auto& command = left.first();
+        if (command.argv.is_empty() && command.redirections.is_empty())
+            return m_right->run(shell);
+    }
+
     auto right = m_right->run(shell)->resolve_as_commands(shell);
 
     Vector<Command> commands;

Shell/AST.h

@@ -699,6 +699,7 @@ private:
     virtual HitTestResult hit_test_position(size_t) override;
     virtual String class_name() const override { return "Sequence"; }
     virtual bool is_list() const override { return true; }
+    virtual bool would_execute() const override { return m_left->would_execute() || m_right->would_execute(); }
 
     RefPtr<Node> m_left;
     RefPtr<Node> m_right;

Shell/Parser.cpp

@@ -717,9 +717,6 @@ RefPtr<AST::Node> Parser::parse_comment()
 
     consume();
     auto text = consume_while(is_not('\n'));
-    if (peek() == '\n')
-        consume();
-
     return create<AST::Comment>(move(text)); // Comment
 }
 

Shell/Shell.cpp

@@ -316,9 +316,6 @@ int Shell::run_command(const StringView& cmd)
     if (cmd.is_empty())
         return 0;
 
-    if (cmd.starts_with("#"))
-        return 0;
-
     auto command = Parser(cmd).parse();
 
     if (!command)
@@ -505,6 +502,8 @@ bool Shell::run_file(const String& filename, bool explicitly_invoked)
     if (file_result.is_error()) {
         if (explicitly_invoked)
             fprintf(stderr, "Failed to open %s: %s\n", filename.characters(), file_result.error().characters());
+        else
+            dbg() << "open() failed for '" << filename << "' with " << file_result.error();
         return false;
     }
     auto file = file_result.value();