Update

autoload/smt2/formatter.vim

@@ -0,0 +1,142 @@
+if polyglot#init#is_disabled(expand('<sfile>:p'), 'smt2', 'autoload/smt2/formatter.vim')
+  finish
+endif
+
+" Formatting requires a rather recent Vim version
+if !((v:version > 802) || (v:version == 802 && has("patch2725")))
+    const s:errmsg_oldvim = "Vim >= 8.2.2725 required for auto-formatting"
+
+    "Dummies
+    function! smt2#formatter#FormatCurrentParagraph()
+        echoerr s:errmsg_oldvim
+    endfunction
+    function! smt2#formatter#FormatAllParagraphs()
+        echoerr s:errmsg_oldvim
+    endfunction
+
+    finish
+endif
+vim9script
+
+# ------------------------------------------------------------------------------
+# Config
+# ------------------------------------------------------------------------------
+# Length of "short" S-expressions
+if !exists("g:smt2_formatter_short_length")
+    g:smt2_formatter_short_length = 80
+endif
+
+# String to use for indentation
+if !exists("g:smt2_formatter_indent_str")
+    g:smt2_formatter_indent_str = '  '
+endif
+
+# ------------------------------------------------------------------------------
+# Formatter
+# ------------------------------------------------------------------------------
+def FitsOneLine(ast: dict<any>): bool
+    # A paragraph with several entries should not be formatted in one line
+    if ast.kind ==# 'Paragraph' && len(ast.value) != 1
+        return false
+    endif
+    return ast.pos_to - ast.pos_from < g:smt2_formatter_short_length && !ast.contains_comment
+enddef
+
+def FormatOneLine(ast: dict<any>): string
+    if ast.kind ==# 'Atom'
+        return ast.value.lexeme
+    elseif ast.kind ==# 'SExpr'
+        var formatted = []
+        for expr in ast.value
+            call formatted->add(expr->FormatOneLine())
+        endfor
+        return '(' .. formatted->join(' ') .. ')'
+    elseif ast.kind ==# 'Paragraph'
+        return ast.value[0]->FormatOneLine()
+    endif
+    throw 'Cannot format AST node: ' .. string(ast)
+    return '' # Unreachable
+enddef
+
+def Format(ast: dict<any>, indent = 0): string
+    const indent_str = repeat(g:smt2_formatter_indent_str, indent)
+
+    if ast.kind ==# 'Atom'
+        return indent_str .. ast.value.lexeme
+    elseif ast.kind ==# 'SExpr'
+        # Short expression -- avoid line breaks
+        if ast->FitsOneLine()
+            return indent_str .. ast->FormatOneLine()
+        endif
+
+        # Long expression -- break lines and indent subexpressions.
+        # Don't break before first subexpression if it's an atom
+        # Note: ast.value->empty() == false; otherwise it would fit in one line
+        var formatted = []
+        if (ast.value[0].kind ==# 'Atom')
+            call formatted->add(ast.value[0]->Format(0))
+        else
+            call formatted->add("\n" .. ast.value[0]->Format(indent + 1))
+        endif
+        for child in ast.value[1 :]
+            call formatted->add(child->Format(indent + 1))
+        endfor
+        return indent_str .. "(" .. formatted->join("\n") .. ")"
+    elseif ast.kind ==# 'Paragraph'
+        var formatted = []
+        for child in ast.value
+            call formatted->add(child->Format())
+        endfor
+        return formatted->join("\n")
+    endif
+    throw 'Cannot format AST node: ' .. string(ast)
+    return '' # Unreachable
+enddef
+
+# ------------------------------------------------------------------------------
+# Public functions
+# ------------------------------------------------------------------------------
+def smt2#formatter#FormatCurrentParagraph()
+    const cursor = getpos('.')
+    const ast = smt2#parser#ParseCurrentParagraph()
+
+    # Identify on which end of the buffer we are (to fix newlines later)
+    silent! normal! {
+    const is_first_paragraph = line('.') == 1
+    silent! normal! }
+    const is_last_paragraph = line('.') == line('$')
+
+    # Replace paragraph by formatted lines
+    const lines = split(Format(ast), '\n')
+    silent! normal! {d}
+    if is_last_paragraph && !is_first_paragraph
+        call append('.', [''] + lines)
+    else
+        call append('.', lines + [''])
+    endif
+
+    # Remove potentially introduced first empty line
+    if is_first_paragraph | silent! :1delete | endif
+
+    # Restore cursor position
+    call setpos('.', cursor)
+enddef
+
+def smt2#formatter#FormatAllParagraphs()
+    const cursor = getpos('.')
+    const asts = smt2#parser#ParseAllParagraphs()
+
+    # Clear buffer & insert formatted paragraphs
+    silent! :1,$delete
+    for ast in asts
+        const lines = split(Format(ast), '\n') + ['']
+        call append('$', lines)
+    endfor
+
+    # Remove first & trailing empty lines
+    silent! :1delete
+    silent! :$delete
+
+    # Restore cursor position
+    call setpos('.', cursor)
+enddef