Add support for a range to toc_depth.

Closes #786.

4 files changed, 85 insertions, 10 deletions

diff --git a/docs/change_log/release-3.1.md b/docs/change_log/release-3.1.md
index 55dde79..b95eb16 100644
--- a/docs/change_log/release-3.1.md
+++ b/docs/change_log/release-3.1.md
@@ -27,6 +27,12 @@ The following new features have been included in the release:
   not valid in HTML5. The `refs` and `backrefs` classes already exist and
   serve the same purpose (#723).
 
+* A new option for `toc_depth` to set not only the bottom section level,
+  but also the top section level. A string consisting of two digits
+  separated by a hyphen in between ("2-5"), defines the top (t) and the
+  bottom (b) (<ht>..<hb>). A single integer still defines the bottom
+  section level (<h1>..<hb>) only. (#787).
+
 ## Bug fixes
 
 The following bug fixes are included in the 3.1 release:
diff --git a/docs/extensions/toc.md b/docs/extensions/toc.md
index f6111b2..ae54cba 100644
--- a/docs/extensions/toc.md
+++ b/docs/extensions/toc.md
@@ -197,9 +197,15 @@ The following options are provided to configure the output:
     Word separator. Character which replaces white space in id. Defaults to "`-`".
 
 * **`toc_depth`**
-    Define up to which section level "n" (`<h1>` to `<hn>`, where `1 <= n <= 6`)
-    to include in the Table of Contents. Defaults to `6`.
-
-    When used with conjunction with `baselevel` this parameter will limit the
-    resulting (adjusted) heading. That is, if both `toc_depth` and `baselevel`
-    are 3, then only the highest level will be present in the table.
+    Define the range of section levels to include in the Table of Contents.
+    A single integer (b) defines the bottom section level (<h1>..<hb>) only.
+    A string consisting of two digits separated by a hyphen in between ("2-5"),
+    define the top (t) and the bottom (b) (<ht>..<hb>). Defaults to `6` (bottom).
+
+    When used with conjunction with `baselevel`, this parameter will not
+    take the fitted hierarchy from `baselevel` into account. That is, if
+    both `toc_depth` and `baselevel` are 3, then only the highest level
+    will be present in the table. If you set `baselevel` to 3 and
+    `toc_depth` to '2-6', the *first* headline will be `<h3>` and so still
+    included in the Table of Contents. To exclude this first level, you
+    have to set `toc_depth` to '4-6'.
\ No newline at end of file
diff --git a/markdown/extensions/toc.py b/markdown/extensions/toc.py
index f6121c2..0985e0f 100644
--- a/markdown/extensions/toc.py
+++ b/markdown/extensions/toc.py
@@ -135,7 +135,11 @@ class TocTreeprocessor(Treeprocessor):
         if self.use_permalinks is None:
             self.use_permalinks = config["permalink"]
         self.header_rgx = re.compile("[Hh][123456]")
-        self.toc_depth = config["toc_depth"]
+        if isinstance(config["toc_depth"], string_type) and '-' in config["toc_depth"]:
+            self.toc_top, self.toc_bottom = [int(x) for x in config["toc_depth"].split('-')]
+        else:
+            self.toc_top = 1
+            self.toc_bottom = int(config["toc_depth"])
 
     def iterparent(self, node):
         ''' Iterator wrapper to get allowed parent and child all at once. '''
@@ -235,7 +239,7 @@ class TocTreeprocessor(Treeprocessor):
         for el in doc.iter():
             if isinstance(el.tag, string_type) and self.header_rgx.match(el.tag):
                 self.set_level(el)
-                if int(el.tag[-1]) > int(self.toc_depth):
+                if int(el.tag[-1]) < self.toc_top or int(el.tag[-1]) > self.toc_bottom:
                     continue
                 text = ''.join(el.itertext()).strip()
 
@@ -296,8 +300,12 @@ class TocExtension(Extension):
                         "Defaults to the headerid ext's slugify function."],
             'separator': ['-', 'Word separator. Defaults to "-".'],
             "toc_depth": [6,
-                          "Define up to which section level n (<h1>..<hn>) to "
-                          "include in the TOC"]
+                          'Define the range of section levels to include in'
+                          'the Table of Contents. A single integer (b) defines'
+                          'the bottom section level (<h1>..<hb>) only.'
+                          'A string consisting of two digits separated by a hyphen'
+                          'in between ("2-5"), define the top (t) and the'
+                          'bottom (b) (<ht>..<hb>). Defaults to `6` (bottom).'],
         }
 
         super(TocExtension, self).__init__(**kwargs)
diff --git a/tests/test_extensions.py b/tests/test_extensions.py
index 2203a78..b4c0779 100644
--- a/tests/test_extensions.py
+++ b/tests/test_extensions.py
@@ -1021,6 +1021,34 @@ class TestTOC(TestCaseWithAssertStartsWith):
             '<h1 id="toc"><em>[TOC]</em></h1>'          # noqa
         )
 
+    def testMinMaxLevel(self):
+        """ Test toc_height setting """
+        md = markdown.Markdown(
+            extensions=[markdown.extensions.toc.TocExtension(toc_depth='3-4')]
+        )
+        text = '# Header 1 not in TOC\n\n## Header 2 not in TOC\n\n### Header 3\n\n####Header 4'
+        self.assertEqual(
+            md.convert(text),
+            '<h1>Header 1 not in TOC</h1>\n'
+            '<h2>Header 2 not in TOC</h2>\n'
+            '<h3 id="header-3">Header 3</h3>\n'
+            '<h4 id="header-4">Header 4</h4>'
+        )
+        self.assertEqual(
+            md.toc,
+            '<div class="toc">\n'
+              '<ul>\n'                                             # noqa
+                '<li><a href="#header-3">Header 3</a>'             # noqa
+                  '<ul>\n'                                         # noqa
+                    '<li><a href="#header-4">Header 4</a></li>\n'  # noqa
+                  '</ul>\n'                                        # noqa
+                '</li>\n'                                          # noqa
+              '</ul>\n'                                            # noqa
+            '</div>\n'
+        )
+
+        self.assertNotIn("Header 1", md.toc)
+
     def testMaxLevel(self):
         """ Test toc_depth setting """
         md = markdown.Markdown(
@@ -1048,6 +1076,33 @@ class TestTOC(TestCaseWithAssertStartsWith):
 
         self.assertNotIn("Header 3", md.toc)
 
+    def testMinMaxLevelwithBaseLevel(self):
+        """ Test toc_height setting together with baselevel """
+        md = markdown.Markdown(
+            extensions=[markdown.extensions.toc.TocExtension(toc_depth='4-6',
+                                                             baselevel=3)]
+        )
+        text = '# First Header\n\n## Second Level\n\n### Third Level'
+        self.assertEqual(
+            md.convert(text),
+            '<h3>First Header</h3>\n'
+            '<h4 id="second-level">Second Level</h4>\n'
+            '<h5 id="third-level">Third Level</h5>'
+        )
+        self.assertEqual(
+            md.toc,
+            '<div class="toc">\n'
+              '<ul>\n'                                                  # noqa
+                '<li><a href="#second-level">Second Level</a>'          # noqa
+                  '<ul>\n'                                              # noqa
+                    '<li><a href="#third-level">Third Level</a></li>\n' # noqa
+                  '</ul>\n'                                             # noqa
+                '</li>\n'                                               # noqa
+              '</ul>\n'                                                 # noqa
+            '</div>\n'
+        )
+        self.assertNotIn("First Header", md.toc)
+
     def testMaxLevelwithBaseLevel(self):
         """ Test toc_depth setting together with baselevel """
         md = markdown.Markdown(