Include comments showing what part a specific node is parsing

README.adoc

@@ -73,6 +73,7 @@ Advanced usage::
 - link:#exiting-with-a-usage-message[Exiting with a usage message]
 - link:#library-mode[Library mode]
 - link:#on-the-fly-parser-generation[On-the-fly parser generation]
+- link:#understanding-the-parser[Understanding the parser]
 
 Developers::
 - link:#testing[Testing]
@@ -314,6 +315,62 @@ Since `docopt.sh` is not patching the script, you also avoid any line number
 jumps in your IDE. However, remember to replace this with the proper parser
 before you ship the script.
 
+=== Understanding the parser
+
+You can turn of minifaction with `-n 0`. This outputs the parser in its full
+form. The parser and the generated AST code is heavily documented and includes
+references to the analyzed DOC, showing what each part does.
+
+e.g. `docopt.sh -n 0 naval_fate.sh`
+
+[source,sh]
+----
+#!/usr/bin/env bash
+
+DOC="Naval Fate.
+  ...
+  --speed=<kn>  Speed in knots [default: 10]."
+# docopt parser below, refresh this parser with `docopt.sh naval_fate.library.sh`
+# shellcheck disable=2016,2086,2317
+docopt() {
+  ...
+  # This is the AST representing the parsed doc. The last node is the root.
+  # Options are first, as mentioned above. The comments above each node is
+  # shows what part of the DOC it is parsing (with line numbers).
+
+  # 03   naval_fate.sh <name> move <x> <y> [--speed=<kn>]
+  #                                         ~~~~~~~
+  node_0(){
+    value __speed 0
+  }
+
+  # 03   naval_fate.sh <name> move <x> <y> [--speed=<kn>]
+  #                    ~~~~~~
+  node_1(){
+    value _name_ a
+  }
+  ...
+  # Unset exported variables from parent shell
+  # that may clash with names derived from the doc
+  for varname in "${varnames[@]}"; do
+    unset "$p$varname"
+  done
+  # Assign internal varnames to output varnames and set defaults
+
+  eval $p'__speed=${var___speed:-10};'\
+  ...
+
+}
+# docopt parser above, complete command for generating this parser is `docopt.sh --line-length=0 naval_fate.library.sh`
+
+naval_fate() {
+  eval "$(docopt "$@")"
+  ...
+}
+naval_fate "$@"
+----
+
+
 === Developers
 
 ==== Testing

docopt_sh/docopt.sh

@@ -27,9 +27,14 @@ docopt() {
   # * argcount (0 or 1)
   # The items are space separated. The order matches the AST node numbering
   options=("OPTIONS")
-  # This is the AST representing the parsed doc.
+  # This is the AST representing the parsed doc. The last node is the root.
+  # Options are first, as mentioned above. The comments above each node is
+  # shows what part of the DOC it is parsing (with line numbers).
+
   "NODES"
 
+  # Exit function that is callable from the parent shell. It outputs an
+  # optional error message and then prints the usage part of the doc
   # shellcheck disable=2016
   cat <<<' docopt_exit() {
   [[ -n $1 ]] && printf "%s\n" "$1" >&2

docopt_sh/parser.py

@@ -71,7 +71,9 @@ def generate(self, script):
       ),
       '"DOC DIGEST"': hashlib.sha256(script.doc.untrimmed_value.encode('utf-8')).hexdigest()[0:5],
       '"OPTIONS"': generate_options_array(leaf_nodes),
-      '  "NODES"': indent('\n'.join(map(str, map(lambda n: ast_cmd(n, nodes), nodes))), level=1),
+      '  "NODES"': indent('\n'.join(
+        map(str, map(lambda n: ast_cmd(n, nodes, script.doc.trimmed_value), nodes))), level=1
+      ),
       '"VARNAMES"': ' '.join([bash_ifs_value(var_name(node)) for node in leaf_nodes]),
       '  "OUTPUT VARNAMES ASSIGNMENTS"': generate_default_assignments(leaf_nodes),
       '  "EARLY RETURN"\n': '' if leaf_nodes else '  return 0\n',
@@ -220,7 +222,7 @@ def helper_name(node):
     return 'switch'
 
 
-def ast_cmd(node, sorted_nodes):
+def ast_cmd(node, sorted_nodes, doc):
   idx = sorted_nodes.index(node)
   if isinstance(node, P.Group):
     if len(sorted_nodes) == 1 and isinstance(node, P.Sequence):
@@ -235,7 +237,9 @@ def ast_cmd(node, sorted_nodes):
       args += ' ' + bash_ifs_value(idx if type(node) is P.Option else f'a:{node.ident}')
     if type(node.default) in [list, int]:
       args += ' true'
-  return Code(f'node_{idx}(){{\n  {helper_name(node)} {args}\n}}\n')
+  # Show where in the DOC the parsing node originates from
+  marked_source = '\n'.join(map(lambda line: f'# {line}', node.mark.show(doc).split('\n')))
+  return Code(f'{marked_source}\nnode_{idx}(){{\n  {helper_name(node)} {args}\n}}\n')
 
 
 def var_name(node):