fix #16206 (#16207)

* better docs and tests
* a bit better only clean trailing whitespace

tests/stdlib/tparsecfg.nim

@@ -5,28 +5,27 @@ discard """
 import parsecfg, streams
 
 when not defined(js):
-  # bug #6046
-  var config = newConfig()
-  config.setSectionKey("foo", "bar", "-1")
-  config.setSectionKey("foo", "foo", "abc")
-
   from stdtest/specialpaths import buildDir
   import os
+  # bug #6046
+  block:
+    var config = newConfig()
+    config.setSectionKey("foo", "bar", "-1")
+    config.setSectionKey("foo", "foo", "abc")
 
-  const file = buildDir / "tparsecfg.ini"
-  config.writeConfig(file)
+    const file = buildDir / "tparsecfg.ini"
+    config.writeConfig(file)
 
-  # file now contains
-  # [foo]
-  # bar=-1
-  # foo=abc
-
-  var config2 = loadConfig(file)
-  let bar = config2.getSectionValue("foo", "bar")
-  let foo = config2.getSectionValue("foo", "foo")
-  assert(bar == "-1")
-  assert(foo == "abc")
+    # file now contains
+    # [foo]
+    # bar=-1
+    # foo=abc
 
+    var config2 = loadConfig(file)
+    let bar = config2.getSectionValue("foo", "bar")
+    let foo = config2.getSectionValue("foo", "foo")
+    assert(bar == "-1")
+    assert(foo == "abc")
 
 ## Creating a configuration file.
 var dict1 = newConfig()
@@ -78,3 +77,59 @@ name=hello
 name=lihf8515
 qq=10214028
 """
+
+block:
+  var dict = loadConfig(newStringStream("""[Simple Values]
+  key=value
+  spaces in keys=allowed
+  spaces in values=allowed as well
+  spaces around the delimiter = obviously
+  you can also use : to delimit keys from values
+  [All Values Are Strings]
+  values like this: 19990429
+  or this: 3.14159265359
+  are they treated as numbers : no
+  integers floats and booleans are held as: strings
+  can use the API to get converted values directly: true
+  [No Values]
+  key_without_value
+  # empty string value is not allowed =
+  [ Seletion A   ]
+  space around section name will be ignored
+  [You can use comments]
+  # like this
+  ; or this
+  # By default only in an empty line.
+  # Inline comments can be harmful because they prevent users
+  # from using the delimiting characters as parts of values.
+  # That being said, this can be customized.
+      [Sections Can Be Indented]
+          can_values_be_as_well = True
+          does_that_mean_anything_special = False
+          purpose = formatting for readability
+          # Did I mention we can indent comments, too?
+  """)
+  )
+
+  let section1 = "Simple Values"
+  doAssert dict.getSectionValue(section1, "key") == "value"
+  doAssert dict.getSectionValue(section1, "spaces in keys") == "allowed"
+  doAssert dict.getSectionValue(section1, "spaces in values") == "allowed as well"
+  doAssert dict.getSectionValue(section1, "spaces around the delimiter") == "obviously"
+  doAssert dict.getSectionValue(section1, "you can also use") == "to delimit keys from values"
+
+  let section2 = "All Values Are Strings"
+  doAssert dict.getSectionValue(section2, "values like this") == "19990429"
+  doAssert dict.getSectionValue(section2, "or this") == "3.14159265359"
+  doAssert dict.getSectionValue(section2, "are they treated as numbers") == "no"
+  doAssert dict.getSectionValue(section2, "integers floats and booleans are held as") == "strings"
+  doAssert dict.getSectionValue(section2, "can use the API to get converted values directly") == "true"
+
+  let section3 = "Seletion A"
+  doAssert dict.getSectionValue(section3, 
+    "space around section name will be ignored", "not an empty value") == ""
+
+  let section4 = "Sections Can Be Indented"
+  doAssert dict.getSectionValue(section4, "can_values_be_as_well") == "True"
+  doAssert dict.getSectionValue(section4, "does_that_mean_anything_special") == "False"
+  doAssert dict.getSectionValue(section4, "purpose") == "formatting for readability"