go/doc/comment: parse and print lists

[This CL is part of a sequence implementing the proposal #51082.
The design doc is at https://go.dev/s/godocfmt-design.]

Implement lists, like:

	Three numbers:

	  - One
	  - Two
	  - Three

For #51082.

Change-Id: Id87d9c19bca677be968f3803809a9ea6c705f3ad
Reviewed-on: https://go-review.googlesource.com/c/go/+/397286
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Reviewed-by: Jonathan Amsterdam <jba@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>

15 files changed, 869 insertions, 5 deletions

diff --git a/src/go/doc/comment/html.go b/src/go/doc/comment/html.go
index 14a20b91e5..bc076f6a58 100644
--- a/src/go/doc/comment/html.go
+++ b/src/go/doc/comment/html.go
@@ -13,6 +13,7 @@ import (
 // An htmlPrinter holds the state needed for printing a Doc as HTML.
 type htmlPrinter struct {
 	*Printer
+	tight bool
 }
 
 // HTML returns an HTML formatting of the Doc.
@@ -33,7 +34,9 @@ func (p *htmlPrinter) block(out *bytes.Buffer, x Block) {
 		fmt.Fprintf(out, "?%T", x)
 
 	case *Paragraph:
-		out.WriteString("<p>")
+		if !p.tight {
+			out.WriteString("<p>")
+		}
 		p.text(out, x.Text)
 		out.WriteString("\n")
 
@@ -56,7 +59,50 @@ func (p *htmlPrinter) block(out *bytes.Buffer, x Block) {
 		out.WriteString("<pre>")
 		p.escape(out, x.Text)
 		out.WriteString("</pre>\n")
+
+	case *List:
+		kind := "ol>\n"
+		if x.Items[0].Number == "" {
+			kind = "ul>\n"
+		}
+		out.WriteString("<")
+		out.WriteString(kind)
+		next := "1"
+		for _, item := range x.Items {
+			out.WriteString("<li")
+			if n := item.Number; n != "" {
+				if n != next {
+					out.WriteString(` value="`)
+					out.WriteString(n)
+					out.WriteString(`"`)
+					next = n
+				}
+				next = inc(next)
+			}
+			out.WriteString(">")
+			p.tight = !x.BlankBetween()
+			for _, blk := range item.Content {
+				p.block(out, blk)
+			}
+			p.tight = false
+		}
+		out.WriteString("</")
+		out.WriteString(kind)
+	}
+}
+
+// inc increments the decimal string s.
+// For example, inc("1199") == "1200".
+func inc(s string) string {
+	b := []byte(s)
+	for i := len(b) - 1; i >= 0; i-- {
+		if b[i] < '9' {
+			b[i]++
+			return string(b)
+		}
+		b[i] = '0'
 	}
+	return "1" + string(b)
 }
 
 // text prints the text sequence x to out.
diff --git a/src/go/doc/comment/markdown.go b/src/go/doc/comment/markdown.go
index 9e86cd8aef..d8550f2e39 100644
--- a/src/go/doc/comment/markdown.go
+++ b/src/go/doc/comment/markdown.go
@@ -66,6 +66,29 @@ func (p *mdPrinter) block(out *bytes.Buffer, x Block) {
 			}
 			out.WriteString("\n")
 		}
+
+	case *List:
+		loose := x.BlankBetween()
+		for i, item := range x.Items {
+			if i > 0 && loose {
+				out.WriteString("\n")
+			}
+			if n := item.Number; n != "" {
+				out.WriteString(" ")
+				out.WriteString(n)
+				out.WriteString(". ")
+			} else {
+				out.WriteString("  - ") // SP SP - SP
+			}
+			for i, blk := range item.Content {
+				const fourSpace = "    "
+				if i > 0 {
+					out.WriteString("\n" + fourSpace)
+				}
+				p.text(out, blk.(*Paragraph).Text)
+				out.WriteString("\n")
+			}
+		}
 	}
 }
 
diff --git a/src/go/doc/comment/parse.go b/src/go/doc/comment/parse.go
index 7f97e41a62..c881bbab5b 100644
--- a/src/go/doc/comment/parse.go
+++ b/src/go/doc/comment/parse.go
@@ -309,6 +309,10 @@ func (p *Parser) Parse(text string) *Doc {
 		case line == "":
 			// emit nothing
 
+		case isList(line):
+			prevWasBlank := len(lines) < len(all) && all[len(all)-len(lines)-1] == ""
+			b, lines = d.list(lines, prevWasBlank)
+
 		case isIndented(line):
 			b, lines = d.code(lines)
 
@@ -575,6 +579,93 @@ func parseLink(line string) (*LinkDef, bool) {
 	return &LinkDef{Text: text, URL: url}, true
 }
 
+// list returns a list built from the indented text at the start of lines,
+// using forceBlankBefore as the value of the List's ForceBlankBefore field.
+// The caller is responsible for ensuring that the first line of lines
+// satisfies isList.
+// list returns the *List as a Block along with the remaining lines.
+func (d *parseDoc) list(lines []string, forceBlankBefore bool) (b Block, rest []string) {
+	lines, rest = indented(lines)
+
+	num, _, _ := listMarker(lines[0])
+	var (
+		list *List = &List{ForceBlankBefore: forceBlankBefore}
+		item *ListItem
+		text []string
+	)
+	flush := func() {
+		if item != nil {
+			if para, _ := d.paragraph(text); para != nil {
+				item.Content = append(item.Content, para)
+			}
+		}
+		text = nil
+	}
+
+	for _, line := range lines {
+		if n, after, ok := listMarker(line); ok && (n != "") == (num != "") {
+			// start new list item
+			flush()
+
+			item = &ListItem{Number: n}
+			list.Items = append(list.Items, item)
+			line = after
+		}
+		line = strings.TrimSpace(line)
+		if line == "" {
+			list.ForceBlankBetween = true
+			flush()
+			continue
+		}
+		text = append(text, strings.TrimSpace(line))
+	}
+	flush()
+	return list, rest
+}
+
+// listMarker parses the line as an indented line beginning with a list marker.
+// If it can do that, it returns the numeric marker ("" for a bullet list),
+// the rest of the line, and ok == true.
+// Otherwise, it returns "", "", false.
+func listMarker(line string) (num, rest string, ok bool) {
+	if !isIndented(line) {
+		return "", "", false
+	}
+	line = strings.TrimSpace(line)
+	if line == "" {
+		return "", "", false
+	}
+
+	// Can we find a marker?
+	if r, n := utf8.DecodeRuneInString(line); r == '•' || r == '*' || r == '+' || r == '-' {
+		num, rest = "", line[n:]
+	} else if '0' <= line[0] && line[0] <= '9' {
+		n := 1
+		for n < len(line) && '0' <= line[n] && line[n] <= '9' {
+			n++
+		}
+		if n >= len(line) || (line[n] != '.' && line[n] != ')') {
+			return "", "", false
+		}
+		num, rest = line[:n], line[n+1:]
+	} else {
+		return "", "", false
+	}
+
+	if !isIndented(rest) || strings.TrimSpace(rest) == "" {
+		return "", "", false
+	}
+
+	return num, rest, true
+}
+
+// isList reports whether the line is the first line of a list,
+// meaning is indented and starts with a list marker.
+func isList(line string) bool {
+	_, _, ok := listMarker(line)
+	return ok
+}
+
 // parseLinkedText parses text that is allowed to contain explicit links,
 // such as [math.Sin] or [Go home page], into a slice of Text items.
 //
diff --git a/src/go/doc/comment/print.go b/src/go/doc/comment/print.go
index d426b81761..cdbc7cc460 100644
--- a/src/go/doc/comment/print.go
+++ b/src/go/doc/comment/print.go
@@ -225,6 +225,29 @@ func (p *commentPrinter) block(out *bytes.Buffer, x Block) {
 			}
 			out.WriteString("\n")
 		}
+
+	case *List:
+		loose := x.BlankBetween()
+		for i, item := range x.Items {
+			if i > 0 && loose {
+				out.WriteString("\n")
+			}
+			out.WriteString(" ")
+			if item.Number == "" {
+				out.WriteString(" - ")
+			} else {
+				out.WriteString(item.Number)
+				out.WriteString(". ")
+			}
+			for i, blk := range item.Content {
+				const fourSpace = "    "
+				if i > 0 {
+					out.WriteString("\n" + fourSpace)
+				}
+				p.text(out, fourSpace, blk.(*Paragraph).Text)
+				out.WriteString("\n")
+			}
+		}
 	}
 }
 
diff --git a/src/go/doc/comment/testdata/list.txt b/src/go/doc/comment/testdata/list.txt
new file mode 100644
index 0000000000..455782f864
--- /dev/null
+++ b/src/go/doc/comment/testdata/list.txt
@@ -0,0 +1,48 @@
+-- input --
+Text.
+- Not a list.
+ - Here is the list.
+     • Using multiple bullets.
+          * Indentation does not matter.
+     + Lots of bullets.
+More text.
+
+-- gofmt --
+Text.
+- Not a list.
+  - Here is the list.
+  - Using multiple bullets.
+  - Indentation does not matter.
+  - Lots of bullets.
+
+More text.
+
+-- text --
+Text. - Not a list.
+  - Here is the list.
+  - Using multiple bullets.
+  - Indentation does not matter.
+  - Lots of bullets.
+
+More text.
+
+-- markdown --
+Text. - Not a list.
+
+  - Here is the list.
+  - Using multiple bullets.
+  - Indentation does not matter.
+  - Lots of bullets.
+
+More text.
+
+-- html --
+<p>Text.
+- Not a list.
+<ul>
+<li>Here is the list.
+<li>Using multiple bullets.
+<li>Indentation does not matter.
+<li>Lots of bullets.
+</ul>
+<p>More text.
diff --git a/src/go/doc/comment/testdata/list2.txt b/src/go/doc/comment/testdata/list2.txt
new file mode 100644
index 0000000000..c390b3d59a
--- /dev/null
+++ b/src/go/doc/comment/testdata/list2.txt
@@ -0,0 +1,57 @@
+-- input --
+Text.
+ 1. Uno
+   2) Dos
+ 3. Tres
+   5. Cinco
+ 7. Siete
+   11. Once
+ 12. Doce
+ 13. Trece.
+
+-- gofmt --
+Text.
+ 1. Uno
+ 2. Dos
+ 3. Tres
+ 5. Cinco
+ 7. Siete
+ 11. Once
+ 12. Doce
+ 13. Trece.
+
+-- text --
+Text.
+ 1. Uno
+ 2. Dos
+ 3. Tres
+ 5. Cinco
+ 7. Siete
+ 11. Once
+ 12. Doce
+ 13. Trece.
+
+-- markdown --
+Text.
+
+ 1. Uno
+ 2. Dos
+ 3. Tres
+ 5. Cinco
+ 7. Siete
+ 11. Once
+ 12. Doce
+ 13. Trece.
+
+-- html --
+<p>Text.
+<ol>
+<li>Uno
+<li>Dos
+<li>Tres
+<li value="5">Cinco
+<li value="7">Siete
+<li value="11">Once
+<li>Doce
+<li>Trece.
+</ol>
diff --git a/src/go/doc/comment/testdata/list3.txt b/src/go/doc/comment/testdata/list3.txt
new file mode 100644
index 0000000000..d7d345d2d3
--- /dev/null
+++ b/src/go/doc/comment/testdata/list3.txt
@@ -0,0 +1,32 @@
+-- input --
+Text.
+
+ 1. Uno
+ 1. Dos
+ 1. Tres
+ 1. Quatro
+
+-- gofmt --
+Text.
+
+ 1. Uno
+ 1. Dos
+ 1. Tres
+ 1. Quatro
+
+-- markdown --
+Text.
+
+ 1. Uno
+ 1. Dos
+ 1. Tres
+ 1. Quatro
+
+-- html --
+<p>Text.
+<ol>
+<li>Uno
+<li value="1">Dos
+<li value="1">Tres
+<li value="1">Quatro
+</ol>
diff --git a/src/go/doc/comment/testdata/list4.txt b/src/go/doc/comment/testdata/list4.txt
new file mode 100644
index 0000000000..9c28d65b6c
--- /dev/null
+++ b/src/go/doc/comment/testdata/list4.txt
@@ -0,0 +1,38 @@
+-- input --
+Text.
+  1. List
+2. Not indented, not a list.
+  3. Another list.
+
+-- gofmt --
+Text.
+ 1. List
+
+2. Not indented, not a list.
+ 3. Another list.
+
+-- text --
+Text.
+ 1. List
+
+2. Not indented, not a list.
+ 3. Another list.
+
+-- markdown --
+Text.
+
+ 1. List
+
+2\. Not indented, not a list.
+
+ 3. Another list.
+
+-- html --
+<p>Text.
+<ol>
+<li>List
+</ol>
+<p>2. Not indented, not a list.
+<ol>
+<li value="3">Another list.
+</ol>
diff --git a/src/go/doc/comment/testdata/list5.txt b/src/go/doc/comment/testdata/list5.txt
new file mode 100644
index 0000000000..a5128e5b7c
--- /dev/null
+++ b/src/go/doc/comment/testdata/list5.txt
@@ -0,0 +1,40 @@
+-- input --
+Text.
+
+  1. One
+  999999999999999999999. Big
+  1000000000000000000000. Bigger
+  1000000000000000000001. Biggest
+
+-- gofmt --
+Text.
+
+ 1. One
+ 999999999999999999999. Big
+ 1000000000000000000000. Bigger
+ 1000000000000000000001. Biggest
+
+-- text --
+Text.
+
+ 1. One
+ 999999999999999999999. Big
+ 1000000000000000000000. Bigger
+ 1000000000000000000001. Biggest
+
+-- markdown --
+Text.
+
+ 1. One
+ 999999999999999999999. Big
+ 1000000000000000000000. Bigger
+ 1000000000000000000001. Biggest
+
+-- html --
+<p>Text.
+<ol>
+<li>One
+<li value="999999999999999999999">Big
+<li>Bigger
+<li>Biggest
+</ol>
diff --git a/src/go/doc/comment/testdata/list6.txt b/src/go/doc/comment/testdata/list6.txt
new file mode 100644
index 0000000000..ffc0122f52
--- /dev/null
+++ b/src/go/doc/comment/testdata/list6.txt
@@ -0,0 +1,129 @@
+-- input --
+Text.
+ - List immediately after.
+ - Another.
+
+More text.
+
+ - List after blank line.
+ - Another.
+
+Even more text.
+ - List immediately after.
+
+ - Blank line between items.
+
+Yet more text.
+
+ - Another list after blank line.
+
+ - Blank line between items.
+
+Still more text.
+ - One list item.
+
+   Multiple paragraphs.
+-- dump --
+Doc
+	Paragraph
+		Plain "Text."
+	List ForceBlankBefore=false ForceBlankBetween=false
+		Item Number=""
+			Paragraph
+				Plain "List immediately after."
+		Item Number=""
+			Paragraph
+				Plain "Another."
+	Paragraph
+		Plain "More text."
+	List ForceBlankBefore=true ForceBlankBetween=false
+		Item Number=""
+			Paragraph
+				Plain "List after blank line."
+		Item Number=""
+			Paragraph
+				Plain "Another."
+	Paragraph
+		Plain "Even more text."
+	List ForceBlankBefore=false ForceBlankBetween=true
+		Item Number=""
+			Paragraph
+				Plain "List immediately after."
+		Item Number=""
+			Paragraph
+				Plain "Blank line between items."
+	Paragraph
+		Plain "Yet more text."
+	List ForceBlankBefore=true ForceBlankBetween=true
+		Item Number=""
+			Paragraph
+				Plain "Another list after blank line."
+		Item Number=""
+			Paragraph
+				Plain "Blank line between items."
+	Paragraph
+		Plain "Still more text."
+	List ForceBlankBefore=false ForceBlankBetween=true
+		Item Number=""
+			Paragraph
+				Plain "One list item."
+			Paragraph
+				Plain "Multiple paragraphs."
+
+-- gofmt --
+Text.
+  - List immediately after.
+  - Another.
+
+More text.
+
+  - List after blank line.
+  - Another.
+
+Even more text.
+
+  - List immediately after.
+
+  - Blank line between items.
+
+Yet more text.
+
+  - Another list after blank line.
+
+  - Blank line between items.
+
+Still more text.
+
+  - One list item.
+
+    Multiple paragraphs.
+
+-- markdown --
+Text.
+
+  - List immediately after.
+  - Another.
+
+More text.
+
+  - List after blank line.
+  - Another.
+
+Even more text.
+
+  - List immediately after.
+
+  - Blank line between items.
+
+Yet more text.
+
+  - Another list after blank line.
+
+  - Blank line between items.
+
+Still more text.
+
+  - One list item.
+
+    Multiple paragraphs.
+
diff --git a/src/go/doc/comment/testdata/list7.txt b/src/go/doc/comment/testdata/list7.txt
new file mode 100644
index 0000000000..446605061f
--- /dev/null
+++ b/src/go/doc/comment/testdata/list7.txt
@@ -0,0 +1,98 @@
+-- input --
+Almost list markers (but not quite):
+
+ -
+
+❦
+
+ - $
+
+❦
+
+ - $
+
+❦
+
+  $
+   $
+
+❦
+
+ 1! List.
+
+❦
+-- gofmt --
+Almost list markers (but not quite):
+
+	-
+
+❦
+
+	- $
+
+❦
+
+	- $
+
+❦
+
+❦
+
+	1! List.
+
+❦
+-- text --
+Almost list markers (but not quite):
+
+	-
+
+❦
+
+	-
+
+❦
+
+	-
+
+❦
+
+❦
+
+	1! List.
+
+❦
+-- markdown --
+Almost list markers (but not quite):
+
+	-
+
+❦
+
+	- $
+
+❦
+
+	- $
+
+❦
+
+❦
+
+	1! List.
+
+❦
+-- html --
+<p>Almost list markers (but not quite):
+<pre>-
+</pre>
+<p>❦
+<pre>- $
+</pre>
+<p>❦
+<pre>- $
+</pre>
+<p>❦
+<p>❦
+<pre>1! List.
+</pre>
+<p>❦
diff --git a/src/go/doc/comment/testdata/list8.txt b/src/go/doc/comment/testdata/list8.txt
new file mode 100644
index 0000000000..fc46b0d835
--- /dev/null
+++ b/src/go/doc/comment/testdata/list8.txt
@@ -0,0 +1,56 @@
+-- input --
+Loose lists.
+  - A
+
+    B
+  - C
+    D
+  - E
+  - F
+-- gofmt --
+Loose lists.
+
+  - A
+
+    B
+
+  - C
+    D
+
+  - E
+
+  - F
+-- text --
+Loose lists.
+
+  - A
+
+    B
+
+  - C D
+
+  - E
+
+  - F
+-- markdown --
+Loose lists.
+
+  - A
+
+    B
+
+  - C D
+
+  - E
+
+  - F
+-- html --
+<p>Loose lists.
+<ul>
+<li><p>A
+<p>B
+<li><p>C
+D
+<li><p>E
+<li><p>F
+</ul>
diff --git a/src/go/doc/comment/testdata/text.txt b/src/go/doc/comment/testdata/text.txt
new file mode 100644
index 0000000000..c4de6e20d2
--- /dev/null
+++ b/src/go/doc/comment/testdata/text.txt
@@ -0,0 +1,62 @@
+{"TextPrefix":"|", "TextCodePrefix": "@"}
+-- input --
+Hello, world
+ Code block here.
+More text.
+Tight list
+ - one
+ - two
+ - three
+Loose list
+ - one
+
+ - two
+
+ - three
+
+# Heading
+
+More text.
+-- gofmt --
+Hello, world
+
+	Code block here.
+
+More text.
+Tight list
+  - one
+  - two
+  - three
+
+Loose list
+
+  - one
+
+  - two
+
+  - three
+
+# Heading
+
+More text.
+-- text --
+|Hello, world
+|
+@Code block here.
+|
+|More text. Tight list
+|  - one
+|  - two
+|  - three
+|
+|Loose list
+|
+|  - one
+|
+|  - two
+|
+|  - three
+|
+|# Heading
+|
+|More text.
diff --git a/src/go/doc/comment/testdata/text8.txt b/src/go/doc/comment/testdata/text8.txt
new file mode 100644
index 0000000000..560ac951c1
--- /dev/null
+++ b/src/go/doc/comment/testdata/text8.txt
@@ -0,0 +1,94 @@
+{"TextWidth": 40}
+-- input --
+If the arguments have version suffixes (like @latest or @v1.0.0), "go install"
+builds packages in module-aware mode, ignoring the go.mod file in the current
+directory or any parent directory, if there is one. This is useful for
+installing executables without affecting the dependencies of the main module.
+To eliminate ambiguity about which module versions are used in the build, the
+arguments must satisfy the following constraints:
+
+ - Arguments must be package paths or package patterns (with "..." wildcards).
+ They must not be standard packages (like fmt), meta-patterns (std, cmd,
+ all), or relative or absolute file paths.
+
+ - All arguments must have the same version suffix. Different queries are not
+ allowed, even if they refer to the same version.
+
+ - All arguments must refer to packages in the same module at the same version.
+
+ - Package path arguments must refer to main packages. Pattern arguments
+ will only match main packages.
+
+ - No module is considered the "main" module. If the module containing
+ packages named on the command line has a go.mod file, it must not contain
+ directives (replace and exclude) that would cause it to be interpreted
+ differently than if it were the main module. The module must not require
+ a higher version of itself.
+
+ - Vendor directories are not used in any module. (Vendor directories are not
+ included in the module zip files downloaded by 'go install'.)
+
+If the arguments don't have version suffixes, "go install" may run in
+module-aware mode or GOPATH mode, depending on the GO111MODULE environment
+variable and the presence of a go.mod file. See 'go help modules' for details.
+If module-aware mode is enabled, "go install" runs in the context of the main
+module.
+-- text --
+If the arguments have version suffixes
+(like @latest or @v1.0.0), "go install"
+builds packages in module-aware mode,
+ignoring the go.mod file in the current
+directory or any parent directory,
+if there is one. This is useful for
+installing executables without affecting
+the dependencies of the main module.
+To eliminate ambiguity about which
+module versions are used in the build,
+the arguments must satisfy the following
+constraints:
+
+  - Arguments must be package paths
+    or package patterns (with "..."
+    wildcards). They must not be
+    standard packages (like fmt),
+    meta-patterns (std, cmd, all),
+    or relative or absolute file paths.
+
+  - All arguments must have the same
+    version suffix. Different queries
+    are not allowed, even if they refer
+    to the same version.
+
+  - All arguments must refer to packages
+    in the same module at the same
+    version.
+
+  - Package path arguments must refer
+    to main packages. Pattern arguments
+    will only match main packages.
+
+  - No module is considered the "main"
+    module. If the module containing
+    packages named on the command line
+    has a go.mod file, it must not
+    contain directives (replace and
+    exclude) that would cause it to be
+    interpreted differently than if it
+    were the main module. The module
+    must not require a higher version of
+    itself.
+
+  - Vendor directories are not used in
+    any module. (Vendor directories are
+    not included in the module zip files
+    downloaded by 'go install'.)
+
+If the arguments don't have version
+suffixes, "go install" may run in
+module-aware mode or GOPATH mode,
+depending on the GO111MODULE environment
+variable and the presence of a go.mod
+file. See 'go help modules' for details.
+If module-aware mode is enabled,
+"go install" runs in the context of the
+main module.
diff --git a/src/go/doc/comment/text.go b/src/go/doc/comment/text.go
index e35e5ccfd1..e9684f066b 100644
--- a/src/go/doc/comment/text.go
+++ b/src/go/doc/comment/text.go
@@ -86,12 +86,12 @@ func (p *textPrinter) block(out *bytes.Buffer, x Block) {
 
 	case *Paragraph:
 		out.WriteString(p.prefix)
-		p.text(out, x.Text)
+		p.text(out, "", x.Text)
 
 	case *Heading:
 		out.WriteString(p.prefix)
 		out.WriteString("# ")
-		p.text(out, x.Text)
+		p.text(out, "", x.Text)
 
 	case *Code:
 		text := x.Text
@@ -104,12 +104,38 @@ func (p *textPrinter) block(out *bytes.Buffer, x Block) {
 			}
 			writeNL(out)
 		}
+
+	case *List:
+		loose := x.BlankBetween()
+		for i, item := range x.Items {
+			if i > 0 && loose {
+				out.WriteString(p.prefix)
+				writeNL(out)
+			}
+			out.WriteString(p.prefix)
+			out.WriteString(" ")
+			if item.Number == "" {
+				out.WriteString(" - ")
+			} else {
+				out.WriteString(item.Number)
+				out.WriteString(". ")
+			}
+			for i, blk := range item.Content {
+				const fourSpace = "    "
+				if i > 0 {
+					writeNL(out)
+					out.WriteString(p.prefix)
+					out.WriteString(fourSpace)
+				}
+				p.text(out, fourSpace, blk.(*Paragraph).Text)
+			}
+		}
 	}
 }
 
 // text prints the text sequence x to out.
 // TODO: Wrap lines.
-func (p *textPrinter) text(out *bytes.Buffer, x []Text) {
+func (p *textPrinter) text(out *bytes.Buffer, indent string, x []Text) {
 	p.oneLongLine(&p.long, x)
 	words := strings.Fields(p.long.String())
 	p.long.Reset()
@@ -118,11 +144,12 @@ func (p *textPrinter) text(out *bytes.Buffer, x []Text) {
 	if p.width < 0 {
 		seq = []int{0, len(words)} // one long line
 	} else {
-		seq = wrap(words, p.width)
+		seq = wrap(words, p.width-utf8.RuneCountInString(indent))
 	}
 	for i := 0; i+1 < len(seq); i++ {
 		if i > 0 {
 			out.WriteString(p.prefix)
+			out.WriteString(indent)
 		}
 		for j, w := range words[seq[i]:seq[i+1]] {
 			if j > 0 {