String arguments can permit arbitrary string values

by leaving out the choices keyword.

docs/markdown/Build-options.md

@@ -16,32 +16,38 @@ Here is a simple option file.
 option('someoption', type : 'string', value : 'optval', description : 'An option')
 option('other_one', type : 'boolean', value : false)
 option('combo_opt', type : 'combo', choices : ['one', 'two', 'three'], value : 'three')
+option('free_array_opt', type : 'array', value : ['one', 'two'])
 option('array_opt', type : 'array', choices : ['one', 'two', 'three'], value : ['one', 'two'])
 ```
 
-All types allow a `description` value to be set describing the option, if no
-option is set then the name of the option will be used instead.
+All types allow a `description` value to be set describing the option,
+if no option is set then the name of the option will be used instead.
 
 ### Strings
 
-The string type is a free form string. If the default value is not set then an
-empty string will be used as the default.
+The string type is a free form string. If the default value is not set
+then an empty string will be used as the default.
 
 ### Booleans
 
-Booleans may have values of either `true` or `false`. If not default value is
-supplied then `true` will be used as the default.
+Booleans may have values of either `true` or `false`. If not default
+value is supplied then `true` will be used as the default.
 
 ### Combos
 
-A combo allows any one of the values in the `choices` parameter to be selected.
-If no default value is set then the first value will be the default.
+A combo allows any one of the values in the `choices` parameter to be
+selected.  If no default value is set then the first value will be the
+default.
 
 ### Arrays
 
-Arrays allow one or more of the values in the `choices` parameter to be selected.
-If the `value` parameter is unset then the values of `choices` will be used as
-the default.
+Arrays represent an array of strings. By default the array can contain
+arbitrary strings. To limit the possible values that can used set the
+`choices` parameter. Meson will then only allow the value array to
+contain strings that are in the given list. The array may be
+empty. The `value` parameter specifies the default value of the option
+and if it is unset then the values of `choices` will be used as the
+default.
 
 This type is new in version 0.44.0
 
@@ -61,9 +67,9 @@ prefix = get_option('prefix')
 ```
 
 It should be noted that you can not set option values in your Meson
-scripts. They have to be set externally with the `meson configure` command
-line tool. Running `meson configure` without arguments in a build dir shows
-you all options you can set.
+scripts. They have to be set externally with the `meson configure`
+command line tool. Running `meson configure` without arguments in a
+build dir shows you all options you can set.
 
 To change their values use the `-D`
 option:
@@ -72,5 +78,26 @@ option:
 $ meson configure -Doption=newvalue
 ```
 
+Setting the value of arrays is a bit special. If you only pass a
+single string, then it is considered to have all values separated by
+commas. Thus invoking the following command:
 
-**NOTE:** If you cannot call `meson configure` you likely have a old version of Meson. In that case you can call `mesonconf` instead, but that is deprecated in newer versions
+```console
+$ meson configure -Darray_opt=foo,bar
+```
+
+would set the value to an array of two elements, `foo` and `bar`.
+
+If you need to have commas in your string values, then you need to
+pass the value with proper shell quoting like this:
+
+```console
+$ meson configure "-Doption=['a,b', 'c,d']"
+```
+
+The inner values must always be single quotes and the outer ones
+double quotes.
+
+**NOTE:** If you cannot call `meson configure` you likely have a old
+  version of Meson. In that case you can call `mesonconf` instead, but
+  that is deprecated in newer versions

docs/markdown/snippets/option-array-type.md

@@ -3,8 +3,9 @@
 Previously to have an option that took more than one value a string value would
 have to be created and split, but validating this was difficult. A new array type
 has been added to the meson_options.txt for this case. It works like a 'combo', but
-allows more than one option to be passed. When used on the command line (with -D),
-values are passed as a comma separated list.
+allows more than one option to be passed. The values can optionally be validated
+against a list of valid values. When used on the command line (with -D), values
+are passed as a comma separated list.
 
 ```meson
 option('array_opt', type : 'array', choices : ['one', 'two', 'three'], value : ['one'])

mesonbuild/coredata.py

@@ -132,7 +132,7 @@ class UserStringArrayOption(UserOption):
 
     def validate(self, value, user_input):
         # User input is for options defined on the command line (via -D
-        # options). Users should put their input in as a comma separated
+        # options). Users can put their input in as a comma separated
         # string, but for defining options in meson_options.txt the format
         # should match that of a combo
         if not user_input:
@@ -144,7 +144,10 @@ class UserStringArrayOption(UserOption):
                 newvalue = value
         else:
             assert isinstance(value, str)
-            newvalue = [v.strip() for v in value.split(',')]
+            if value.startswith('['):
+                newvalue = ast.literal_eval(value)
+            else:
+                newvalue = [v.strip() for v in value.split(',')]
         if not isinstance(newvalue, list):
             raise MesonException('"{0}" should be a string array, but it is not'.format(str(newvalue)))
         for i in newvalue:

mesonbuild/optinterpreter.py

@@ -86,15 +86,17 @@ def ComboParser(name, description, kwargs):
 
 @permitted_kwargs({'value', 'choices'})
 def string_array_parser(name, description, kwargs):
-    if 'choices' not in kwargs:
-        raise OptionException('Array option missing "choices" keyword.')
-    choices = kwargs['choices']
-    if not isinstance(choices, list):
-        raise OptionException('Array choices must be an array.')
-    for i in choices:
-        if not isinstance(i, str):
-            raise OptionException('Array choice elements must be strings.')
-    value = kwargs.get('value', choices)
+    if 'choices' in kwargs:
+        choices = kwargs['choices']
+        if not isinstance(choices, list):
+            raise OptionException('Array choices must be an array.')
+        for i in choices:
+            if not isinstance(i, str):
+                raise OptionException('Array choice elements must be strings.')
+            value = kwargs.get('value', choices)
+    else:
+        choices = None
+        value = kwargs.get('value', [])
     if not isinstance(value, list):
         raise OptionException('Array choices must be passed as an array.')
     return coredata.UserStringArrayOption(name, description, value, choices=choices)

run_unittests.py

@@ -1611,6 +1611,25 @@ int main(int argc, char **argv) {
         changed = get_opt()
         self.assertDictEqual(changed, expected)
 
+    def opt_has(self, name, value):
+        res = self.introspect('--buildoptions')
+        found = False
+        for i in res:
+            if i['name'] == name:
+                self.assertEqual(i['value'], value)
+                found = True
+                break
+        self.assertTrue(found, "Array option not found in introspect data.")
+
+    def test_free_stringarray_setting(self):
+        testdir = os.path.join(self.common_test_dir, '47 options')
+        self.init(testdir)
+        self.opt_has('free_array_opt', [])
+        self.setconf('-Dfree_array_opt=foo,bar', will_build=False)
+        self.opt_has('free_array_opt', ['foo', 'bar'])
+        self.setconf("-Dfree_array_opt=['a,b', 'c,d']", will_build=False)
+        self.opt_has('free_array_opt', ['a,b', 'c,d'])
+
 
 class FailureTests(BasePlatformTests):
     '''

test cases/common/47 options/meson_options.txt

@@ -2,3 +2,4 @@ option('testoption', type : 'string', value : 'optval', description : 'An option
 option('other_one', type : 'boolean', value : false)
 option('combo_opt', type : 'combo', choices : ['one', 'two', 'combo'], value : 'combo')
 option('array_opt', type : 'array', choices : ['one', 'two', 'three'], value : ['one', 'two'])
+option('free_array_opt', type : 'array')