Improve rust comment closing handling

/// foo
    ///%( )

    /// foo
    /// %( )

With `c<ret>bar<esc>`,

    /// foo
    bar

    /// foo
    ///
    /// bar

Based on c-family block comment handling, this patch also add rust
block comment indentation.

This affects `o` behavior on empty comment but it allows a way more
efficient way to clear comments.

rc/filetype/rust.kak

@@ -99,9 +99,52 @@ define-command -hidden rust-trim-indent %{
 
 define-command -hidden rust-indent-on-new-line %~
     evaluate-commands -draft -itersel %<
-        # copy // comments prefix and following white spaces
         try %{
-            execute-keys -draft k <a-x> s ^\h*//[!/]{0,2}\h* <ret> y gh j P
+            try %[ # line comment
+                evaluate-commands -draft -save-regs '/"' %[
+                    # copy the commenting prefix
+                    execute-keys -save-regs '' k <a-x> s ^\h*//[!/]{0,2}\h* <ret> y
+                    try %[
+                        # if the previous comment isn't empty, create a new one
+                        execute-keys <a-x><a-K>^\h*//[!/]{0,2}$<ret> j<a-x>s^\h*<ret>P
+                    ] catch %[
+                        # TODO figure out a way to not delete empty comment in current line
+                        # if there is no space and text in the previous comment, remove it completely
+                        execute-keys s //.*<ret> d
+                    ]
+                ]
+            ] catch %[ # block comment
+                # if the previous line isn't within a comment scope, break
+                execute-keys -draft k<a-x> <a-k>^(\h*/\*|\h+\*(?!/))<ret>
+
+                # find comment opening, validate it was not closed, and check its using star prefixes
+                execute-keys -draft <a-?>/\*<ret><a-H> <a-K>\*/<ret> <a-k>\A\h*/\*([^\n]*\n\h*\*)*[^\n]*\n\h*.\z<ret>
+
+                try %[
+                    # if the previous line is opening the comment, insert star preceeded by space
+                    execute-keys -draft k<a-x><a-k>^\h*/\*<ret>
+                    execute-keys -draft i*<space><esc>
+                ] catch %[
+                    try %[
+                        # if the next line is a comment line insert a star
+                        execute-keys -draft j<a-x><a-k>^\h+\*<ret>
+                        execute-keys -draft i*<space><esc>
+                    ] catch %[
+                        try %[
+                            # if the previous line is an empty comment line, close the comment scope
+                            execute-keys -draft k<a-x><a-k>^\h+\*\h+$<ret> <a-x>1s\*(\h*)<ret>c/<esc>
+                        ] catch %[
+                            # if the previous line is a non-empty comment line, add a star
+                            execute-keys -draft i*<space><esc>
+                        ]
+                    ]
+                ]
+
+                # trim trailing whitespace on the previous line
+                try %[ execute-keys -draft s\h+$<ret> d ]
+                # align the new star with the previous one
+                execute-keys K<a-x>1s^[^*]*(\*)<ret>&
+            ]
         } catch %`
             # preserve previous line indent
             try %{ execute-keys -draft <semicolon> K <a-&> }

test/indent/rust/block-comment-close/in

@@ -0,0 +1,6 @@
+    /* foo
+     * %( )
+
+    /* foo
+     *%( )
+

test/indent/rust/block-comment-close/out

@@ -0,0 +1,8 @@
+    /* foo
+     */
+bar
+
+    /* foo
+     *
+     * bar
+

test/indent/rust/block-comment/cmd

@@ -0,0 +1 @@
+c<ret>bar<esc>

test/indent/rust/block-comment/in

@@ -0,0 +1,12 @@
+    /* foo%( )
+
+    /*! foo%( )
+
+    /*!! foo%( )
+
+    /** foo%( )
+
+    /*** foo%( )
+
+    println!("hello world"); /* foo%( )
+

test/indent/rust/block-comment/out

@@ -0,0 +1,18 @@
+    /* foo
+     * bar
+
+    /*! foo
+     * bar
+
+    /*!! foo
+     * bar
+
+    /** foo
+     * bar
+
+    /*** foo
+     * bar
+
+    println!("hello world"); /* foo
+    bar
+

test/indent/rust/block-comment/rc

@@ -0,0 +1,3 @@
+source "%val{runtime}/colors/default.kak"
+source "%val{runtime}/rc/filetype/rust.kak"
+set buffer filetype rust

test/indent/rust/line-comment-close/cmd

@@ -0,0 +1 @@
+c<ret>bar<esc>

test/indent/rust/line-comment-close/in

@@ -0,0 +1,26 @@
+    // foo
+    // %( )
+
+    // foo
+    //%( )
+
+    //! %( )
+
+    //!%( )
+
+    //!! %( )
+
+    //!!%( )
+
+    /// %( )
+
+    ///%( )
+
+    //// %( )
+
+    ////%( )
+
+    println!("hello world"); // %( )
+
+    println!("hello world"); //%( )
+

test/indent/rust/line-comment-close/out

@@ -0,0 +1,33 @@
+    // foo
+    //
+    // bar
+
+    // foo
+    bar
+
+    //!
+    //! bar
+
+    bar
+
+    //!!
+    //!! bar
+
+    bar
+
+    ///
+    /// bar
+
+    bar
+
+    ////
+    //// bar
+
+    bar
+
+    println!("hello world"); //
+    bar
+
+    println!("hello world"); //
+    bar
+

test/indent/rust/line-comment-close/rc

@@ -0,0 +1,3 @@
+source "%val{runtime}/colors/default.kak"
+source "%val{runtime}/rc/filetype/rust.kak"
+set buffer filetype rust

test/indent/rust/line-comment/cmd

@@ -0,0 +1 @@
+c<ret>bar<esc>

test/indent/rust/line-comment/rc

@@ -0,0 +1,3 @@
+source "%val{runtime}/colors/default.kak"
+source "%val{runtime}/rc/filetype/rust.kak"
+set buffer filetype rust