Add range() function

Fixes: #5026.

data/syntax-highlighting/vim/syntax/meson.vim

@@ -119,6 +119,7 @@ syn keyword mesonBuiltin
   \ test
   \ vcs_tag
   \ warning
+  \ range
 
 if exists("meson_space_error_highlight")
   " trailing whitespace

docs/markdown/Reference-manual.md

@@ -1861,6 +1861,36 @@ which to build the targets.
 If you desire more specific behavior than what this command provides,
 you should use `custom_target`.
 
+### range()
+
+``` meson
+    rangeobject range(stop)
+    rangeobject range(start, stop[, step])
+```
+
+*Since 0.58.0*
+
+Return an opaque object that can be only be used in `foreach` statements.
+- `start` must be integer greater or equal to 0. Defaults to 0.
+- `stop` must be integer greater or equal to `start`.
+- `step` must be integer greater or equal to 1. Defaults to 1.
+
+It cause the `foreach` loop to be called with the value from `start` included
+to `stop` excluded with an increment of `step` after each loop.
+
+```meson
+# Loop 15 times with i from 0 to 14 included.
+foreach i : range(15)
+   ...
+endforeach
+```
+
+The range object can also be assigned to a variable and indexed.
+```meson
+r = range(5, 10, 2)
+assert(r[2] == 9)
+```
+
 ## Built-in objects
 
 These are built-in objects that are always available.

docs/markdown/snippets/range.md

@@ -0,0 +1,28 @@
+## New `range()` function
+
+``` meson
+    rangeobject range(stop)
+    rangeobject range(start, stop[, step])
+```
+
+Return an opaque object that can be only be used in `foreach` statements.
+- `start` must be integer greater or equal to 0. Defaults to 0.
+- `stop` must be integer greater or equal to `start`.
+- `step` must be integer greater or equal to 1. Defaults to 1.
+
+It cause the `foreach` loop to be called with the value from `start` included
+to `stop` excluded with an increment of `step` after each loop.
+
+```meson
+# Loop 15 times with i from 0 to 14 included.
+foreach i : range(15)
+   ...
+endforeach
+```
+
+The range object can also be assigned to a variable and indexed.
+```meson
+r = range(5, 10, 2)
+assert(r[2] == 9)
+```
+

mesonbuild/ast/interpreter.py

@@ -128,6 +128,7 @@ class AstInterpreter(interpreterbase.InterpreterBase):
                            'subdir_done': self.func_do_nothing,
                            'alias_target': self.func_do_nothing,
                            'summary': self.func_do_nothing,
+                           'range': self.func_do_nothing,
                            })
 
     def func_do_nothing(self, node: BaseNode, args: T.List[TYPE_nvar], kwargs: T.Dict[str, TYPE_nvar]) -> bool:

mesonbuild/interpreter.py

@@ -30,7 +30,7 @@ from .interpreterbase import check_stringlist, flatten, noPosargs, noKwargs, str
 from .interpreterbase import InterpreterException, InvalidArguments, InvalidCode, SubdirDoneRequest
 from .interpreterbase import InterpreterObject, MutableInterpreterObject, Disabler, disablerIfNotFound
 from .interpreterbase import FeatureNew, FeatureDeprecated, FeatureNewKwargs, FeatureDeprecatedKwargs
-from .interpreterbase import ObjectHolder, MesonVersionString
+from .interpreterbase import ObjectHolder, MesonVersionString, RangeHolder
 from .interpreterbase import TYPE_var, TYPE_nkwargs
 from .modules import ModuleReturnValue, ModuleObject, ModuleState
 from .cmake import CMakeInterpreter
@@ -2509,7 +2509,8 @@ class Interpreter(InterpreterBase):
                            'static_library': self.func_static_lib,
                            'both_libraries': self.func_both_lib,
                            'test': self.func_test,
-                           'vcs_tag': self.func_vcs_tag
+                           'vcs_tag': self.func_vcs_tag,
+                           'range': self.func_range,
                            })
         if 'MESON_UNIT_TEST' in os.environ:
             self.funcs.update({'exception': self.func_exception})
@@ -5033,3 +5034,24 @@ This will become a hard error in the future.''', location=self.current_node)
             raise InvalidCode('Is_disabler takes one argument.')
         varname = args[0]
         return isinstance(varname, Disabler)
+
+    @noKwargs
+    @FeatureNew('range', '0.58.0')
+    @typed_pos_args('range', int, optargs=[int, int])
+    def func_range(self, node, args: T.Tuple[int, T.Optional[int], T.Optional[int]], kwargs: T.Dict[str, T.Any]) -> RangeHolder:
+        start, stop, step = args
+        # Just like Python's range, we allow range(stop), range(start, stop), or
+        # range(start, stop, step)
+        if stop is None:
+            stop = start
+            start = 0
+        if step is None:
+            step = 1
+        # This is more strict than Python's range()
+        if start < 0:
+            raise InterpreterException('start cannot be negative')
+        if stop < start:
+            raise InterpreterException('stop cannot be less than start')
+        if step < 1:
+            raise InterpreterException('step must be >=1')
+        return RangeHolder(start, stop, step)

mesonbuild/interpreterbase.py

@@ -70,6 +70,20 @@ class ObjectHolder(T.Generic[TV_InterpreterObject]):
 class MesonVersionString(str):
     pass
 
+class RangeHolder(InterpreterObject):
+    def __init__(self, start: int, stop: int, step: int) -> None:
+        super().__init__()
+        self.range = range(start, stop, step)
+
+    def __iter__(self) -> T.Iterator[int]:
+        return iter(self.range)
+
+    def __getitem__(self, key: int) -> int:
+        return self.range[key]
+
+    def __len__(self) -> int:
+        return len(self.range)
+
 # Decorators for method calls.
 
 def check_stringlist(a: T.Any, msg: str = 'Arguments must be strings.') -> None:
@@ -950,7 +964,7 @@ The result of this is undefined and will become a hard error in a future Meson r
         assert(isinstance(node, mparser.ForeachClauseNode))
         items = self.evaluate_statement(node.items)
 
-        if isinstance(items, list):
+        if isinstance(items, (list, RangeHolder)):
             if len(node.varnames) != 1:
                 raise InvalidArguments('Foreach on array does not unpack')
             varname = node.varnames[0]

test cases/common/61 foreach/meson.build

@@ -31,3 +31,23 @@ foreach i : items
 endforeach
 
 assert(result == ['a', 'b'], 'Continue or break in foreach failed')
+
+items = []
+iter = range(2)
+foreach i : iter
+  items += i
+endforeach
+assert(items == [0, 1])
+assert(iter[1] == 1)
+
+items = []
+foreach i : range(1, 2)
+  items += i
+endforeach
+assert(items == [1])
+
+items = []
+foreach i : range(1, 10, 2)
+  items += i
+endforeach
+assert(items == [1, 3, 5, 7, 9])