Merge pull request #3490 from MathieuDuponchelle/dict_builtin

Add new built-in type, dict

9 files changed, 284 insertions, 26 deletions

diff --git a/docs/markdown/Reference-manual.md b/docs/markdown/Reference-manual.md
index 1e0e4c9..6c20221 100644
--- a/docs/markdown/Reference-manual.md
+++ b/docs/markdown/Reference-manual.md
@@ -1737,6 +1737,23 @@ The following methods are defined for all [arrays](Syntax.md#arrays):
 You can also iterate over arrays with the [`foreach`
 statement](Syntax.md#foreach-statements).
 
+### `dictionary` object
+
+The following methods are defined for all [dictionaries](Syntax.md#dictionaries):
+
+- `has_key(key)` returns `true` if the dictionary contains the key
+  given as argument, `false` otherwise
+
+- `get(key, fallback)`, returns the value for the key given as first argument
+  if it is present in the dictionary, or the optional fallback value given
+  as the second argument. If a single argument was given and the key was not
+  found, causes a fatal error
+
+You can also iterate over dictionaries with the [`foreach`
+statement](Syntax.md#foreach-statements).
+
+Dictionaries are available since 0.47.0.
+
 ## Returned objects
 
 These are objects returned by the [functions listed above](#functions).
diff --git a/docs/markdown/Syntax.md b/docs/markdown/Syntax.md
index 30eedf8..42002f4 100644
--- a/docs/markdown/Syntax.md
+++ b/docs/markdown/Syntax.md
@@ -284,6 +284,31 @@ The following methods are defined for all arrays:
  - `contains`, returns `true` if the array contains the object given as argument, `false` otherwise
  - `get`, returns the object at the given index, negative indices count from the back of the array, indexing out of bounds is a fatal error. Provided for backwards-compatibility, it is identical to array indexing.
 
+Dictionaries
+--
+
+Dictionaries are delimited by curly braces. A dictionary can contain an
+arbitrary number of key value pairs. Keys are required to be literal
+strings, values can be objects of any type.
+
+```meson
+my_dict = {'foo': 42, 'bar': 'baz'}
+```
+
+Keys must be unique:
+
+```meson
+# This will fail
+my_dict = {'foo': 42, 'foo': 43}
+```
+
+Dictionaries are immutable.
+
+Dictionaries are available since 0.47.0.
+
+Visit the [Reference Manual](Reference-manual.md#dictionary-object) to read
+about the methods exposed by dictionaries.
+
 Function calls
 --
 
@@ -329,9 +354,17 @@ endif
 
 ## Foreach statements
 
-To do an operation on all elements of an array, use the `foreach`
-command. As an example, here's how you would define two executables
-with corresponding tests.
+To do an operation on all elements of an iterable, use the `foreach`
+command.
+
+> Note that Meson variables are immutable. Trying to assign a new value
+> to the iterated object inside a foreach loop will not affect foreach's
+> control flow.
+
+### Foreach with an array
+
+Here's an example of how you could define two executables
+with corresponding tests using arrays and foreach.
 
 ```meson
 progs = [['prog1', ['prog1.c', 'foo.c']],
@@ -343,9 +376,31 @@ foreach p : progs
 endforeach
 ```
 
-Note that Meson variables are immutable. Trying to assign a new value
-to `progs` inside a foreach loop will not affect foreach's control
-flow.
+### Foreach with a dictionary
+
+Here's an example of you could iterate a set of components that
+should be compiled in according to some configuration. This uses
+a [dictionary][dictionaries], which is available since 0.47.0.
+
+```meson
+components = {
+  'foo': ['foo.c'],
+  'bar': ['bar.c'],
+  'baz:' ['baz.c'],
+}
+
+# compute a configuration based on system dependencies, custom logic
+conf = configuration_data()
+conf.set('USE_FOO', 1)
+
+# Determine the sources to compile
+sources_to_compile = []
+foreach name, sources : components
+  if conf.get('USE_@0@'.format(name.to_upper()), 0) == 1
+    sources_to_compile += sources
+  endif
+endforeach
+```
 
 Logical operations
 --
diff --git a/docs/markdown/snippets/dict_builtin.md b/docs/markdown/snippets/dict_builtin.md
new file mode 100644
index 0000000..1bd24ce
--- /dev/null
+++ b/docs/markdown/snippets/dict_builtin.md
@@ -0,0 +1,19 @@
+## New built-in object dictionary
+
+Meson dictionaries use a syntax similar to python's dictionaries,
+but have a narrower scope: they are immutable, keys can only
+be string literals, and initializing a dictionary with duplicate
+keys causes a fatal error.
+
+Example usage:
+
+```meson
+dict = {'foo': 42, 'bar': 'baz'}
+
+foo = dict.get('foo')
+foobar = dict.get('foobar', 'fallback-value')
+
+foreach key, value : dict
+  Do something with key and value
+endforeach
+```
diff --git a/mesonbuild/interpreter.py b/mesonbuild/interpreter.py
index 070845b..a63c143 100644
--- a/mesonbuild/interpreter.py
+++ b/mesonbuild/interpreter.py
@@ -45,6 +45,8 @@ permitted_method_kwargs = {
 def stringifyUserArguments(args):
     if isinstance(args, list):
         return '[%s]' % ', '.join([stringifyUserArguments(x) for x in args])
+    elif isinstance(args, dict):
+        return '{%s}' % ', '.join(['%s : %s' % (stringifyUserArguments(k), stringifyUserArguments(v)) for k, v in args.items()])
     elif isinstance(args, int):
         return str(args)
     elif isinstance(args, str):
@@ -2283,6 +2285,8 @@ to directly access options of other subprojects.''')
         arg = posargs[0]
         if isinstance(arg, list):
             argstr = stringifyUserArguments(arg)
+        elif isinstance(arg, dict):
+            argstr = stringifyUserArguments(arg)
         elif isinstance(arg, str):
             argstr = arg
         elif isinstance(arg, int):
diff --git a/mesonbuild/interpreterbase.py b/mesonbuild/interpreterbase.py
index 60b0465..9f323d1 100644
--- a/mesonbuild/interpreterbase.py
+++ b/mesonbuild/interpreterbase.py
@@ -265,6 +265,8 @@ class InterpreterBase:
             return self.evaluate_comparison(cur)
         elif isinstance(cur, mparser.ArrayNode):
             return self.evaluate_arraystatement(cur)
+        elif isinstance(cur, mparser.DictNode):
+            return self.evaluate_dictstatement(cur)
         elif isinstance(cur, mparser.NumberNode):
             return cur.value
         elif isinstance(cur, mparser.AndNode):
@@ -296,6 +298,11 @@ class InterpreterBase:
             raise InvalidCode('Keyword arguments are invalid in array construction.')
         return arguments
 
+    def evaluate_dictstatement(self, cur):
+        (arguments, kwargs) = self.reduce_arguments(cur.args)
+        assert (not arguments)
+        return kwargs
+
     def evaluate_notstatement(self, cur):
         v = self.evaluate_statement(cur.value)
         if not isinstance(v, bool):
@@ -444,15 +451,28 @@ The result of this is undefined and will become a hard error in a future Meson r
 
     def evaluate_foreach(self, node):
         assert(isinstance(node, mparser.ForeachClauseNode))
-        varname = node.varname.value
         items = self.evaluate_statement(node.items)
-        if is_disabler(items):
-            return items
-        if not isinstance(items, list):
-            raise InvalidArguments('Items of foreach loop is not an array')
-        for item in items:
-            self.set_variable(varname, item)
-            self.evaluate_codeblock(node.block)
+
+        if isinstance(items, list):
+            if len(node.varnames) != 1:
+                raise InvalidArguments('Foreach on array does not unpack')
+            varname = node.varnames[0].value
+            if is_disabler(items):
+                return items
+            for item in items:
+                self.set_variable(varname, item)
+                self.evaluate_codeblock(node.block)
+        elif isinstance(items, dict):
+            if len(node.varnames) != 2:
+                raise InvalidArguments('Foreach on dict unpacks key and value')
+            if is_disabler(items):
+                return items
+            for key, value in items.items():
+                self.set_variable(node.varnames[0].value, key)
+                self.set_variable(node.varnames[1].value, value)
+                self.evaluate_codeblock(node.block)
+        else:
+            raise InvalidArguments('Items of foreach loop must be an array or a dict')
 
     def evaluate_plusassign(self, node):
         assert(isinstance(node, mparser.PlusAssignmentNode))
@@ -491,12 +511,21 @@ The result of this is undefined and will become a hard error in a future Meson r
             raise InterpreterException(
                 'Tried to index an object that doesn\'t support indexing.')
         index = self.evaluate_statement(node.index)
-        if not isinstance(index, int):
-            raise InterpreterException('Index value is not an integer.')
-        try:
-            return iobject[index]
-        except IndexError:
-            raise InterpreterException('Index %d out of bounds of array of size %d.' % (index, len(iobject)))
+
+        if isinstance(iobject, dict):
+            if not isinstance(index, str):
+                raise InterpreterException('Key is not a string')
+            try:
+                return iobject[index]
+            except KeyError:
+                raise InterpreterException('Key %s is not in dict' % index)
+        else:
+            if not isinstance(index, int):
+                raise InterpreterException('Index value is not an integer.')
+            try:
+                return iobject[index]
+            except IndexError:
+                raise InterpreterException('Index %d out of bounds of array of size %d.' % (index, len(iobject)))
 
     def function_call(self, node):
         func_name = node.func_name
@@ -529,6 +558,8 @@ The result of this is undefined and will become a hard error in a future Meson r
             return self.int_method_call(obj, method_name, args)
         if isinstance(obj, list):
             return self.array_method_call(obj, method_name, args)
+        if isinstance(obj, dict):
+            return self.dict_method_call(obj, method_name, args)
         if isinstance(obj, mesonlib.File):
             raise InvalidArguments('File object "%s" is not callable.' % obj)
         if not isinstance(obj, InterpreterObject):
@@ -687,6 +718,43 @@ The result of this is undefined and will become a hard error in a future Meson r
         m = 'Arrays do not have a method called {!r}.'
         raise InterpreterException(m.format(method_name))
 
+    def dict_method_call(self, obj, method_name, args):
+        (posargs, kwargs) = self.reduce_arguments(args)
+        if is_disabled(posargs, kwargs):
+            return Disabler()
+
+        if method_name in ('has_key', 'get'):
+            if method_name == 'has_key':
+                if len(posargs) != 1:
+                    raise InterpreterException('has_key() takes exactly one argument.')
+            else:
+                if len(posargs) not in (1, 2):
+                    raise InterpreterException('get() takes one or two arguments.')
+
+            key = posargs[0]
+            if not isinstance(key, (str)):
+                raise InvalidArguments('Dictionary key must be a string.')
+
+            has_key = key in obj
+
+            if method_name == 'has_key':
+                return has_key
+
+            if has_key:
+                return obj[key]
+
+            if len(posargs) == 2:
+                return posargs[1]
+
+            raise InterpreterException('Key {!r} is not in the dictionary.'.format(key))
+
+        if method_name == 'keys':
+            if len(posargs) != 0:
+                raise InterpreterException('keys() takes no arguments.')
+            return list(obj.keys())
+
+        raise InterpreterException('Dictionaries do not have a method called "%s".' % method_name)
+
     def reduce_arguments(self, args):
         assert(isinstance(args, mparser.ArgumentNode))
         if args.incorrect_order():
@@ -741,7 +809,7 @@ To specify a keyword argument, use : instead of =.''')
 
     def is_assignable(self, value):
         return isinstance(value, (InterpreterObject, dependencies.Dependency,
-                                  str, int, list, mesonlib.File))
+                                  str, int, list, dict, mesonlib.File))
 
     def is_elementary_type(self, v):
         return isinstance(v, (int, float, str, bool, list))
diff --git a/mesonbuild/mparser.py b/mesonbuild/mparser.py
index 8cef377..78683be 100644
--- a/mesonbuild/mparser.py
+++ b/mesonbuild/mparser.py
@@ -104,6 +104,8 @@ class Lexer:
             ('rparen', re.compile(r'\)')),
             ('lbracket', re.compile(r'\[')),
             ('rbracket', re.compile(r'\]')),
+            ('lcurl', re.compile(r'\{')),
+            ('rcurl', re.compile(r'\}')),
             ('dblquote', re.compile(r'"')),
             ('string', re.compile(r"'([^'\\]|(\\.))*'")),
             ('comma', re.compile(r',')),
@@ -134,6 +136,7 @@ class Lexer:
         loc = 0
         par_count = 0
         bracket_count = 0
+        curl_count = 0
         col = 0
         while loc < len(self.code):
             matched = False
@@ -160,6 +163,10 @@ class Lexer:
                         bracket_count += 1
                     elif tid == 'rbracket':
                         bracket_count -= 1
+                    elif tid == 'lcurl':
+                        curl_count += 1
+                    elif tid == 'rcurl':
+                        curl_count -= 1
                     elif tid == 'dblquote':
                         raise ParseException('Double quotes are not supported. Use single quotes.', self.getline(line_start), lineno, col)
                     elif tid == 'string':
@@ -187,7 +194,7 @@ This will become a hard error in a future Meson release.""", self.getline(line_s
                     elif tid == 'eol' or tid == 'eol_cont':
                         lineno += 1
                         line_start = loc
-                        if par_count > 0 or bracket_count > 0:
+                        if par_count > 0 or bracket_count > 0 or curl_count > 0:
                             break
                     elif tid == 'id':
                         if match_text in self.keywords:
@@ -241,6 +248,13 @@ class ArrayNode:
         self.colno = args.colno
         self.args = args
 
+class DictNode:
+    def __init__(self, args):
+        self.subdir = args.subdir
+        self.lineno = args.lineno
+        self.colno = args.colno
+        self.args = args
+
 class EmptyNode:
     def __init__(self, lineno, colno):
         self.subdir = ''
@@ -340,10 +354,10 @@ class PlusAssignmentNode:
         self.value = value
 
 class ForeachClauseNode:
-    def __init__(self, lineno, colno, varname, items, block):
+    def __init__(self, lineno, colno, varnames, items, block):
         self.lineno = lineno
         self.colno = colno
-        self.varname = varname
+        self.varnames = varnames
         self.items = items
         self.block = block
 
@@ -601,6 +615,10 @@ class Parser:
             args = self.args()
             self.block_expect('rbracket', block_start)
             return ArrayNode(args)
+        elif self.accept('lcurl'):
+            key_values = self.key_values()
+            self.block_expect('rcurl', block_start)
+            return DictNode(key_values)
         else:
             return self.e9()
 
@@ -618,6 +636,31 @@ class Parser:
             return StringNode(t)
         return EmptyNode(self.current.lineno, self.current.colno)
 
+    def key_values(self):
+        s = self.statement()
+        a = ArgumentNode(s)
+
+        while not isinstance(s, EmptyNode):
+            potential = self.current
+            if self.accept('colon'):
+                if not isinstance(s, StringNode):
+                    raise ParseException('Key must be a string.',
+                                         self.getline(), s.lineno, s.colno)
+                if s.value in a.kwargs:
+                    # + 1 to colno to point to the actual string, not the opening quote
+                    raise ParseException('Duplicate dictionary key: {}'.format(s.value),
+                                         self.getline(), s.lineno, s.colno + 1)
+                a.set_kwarg(s.value, self.statement())
+                potential = self.current
+                if not self.accept('comma'):
+                    return a
+                a.commas.append(potential)
+            else:
+                raise ParseException('Only key:value pairs are valid in dict construction.',
+                                     self.getline(), s.lineno, s.colno)
+            s = self.statement()
+        return a
+
     def args(self):
         s = self.statement()
         a = ArgumentNode(s)
@@ -629,7 +672,7 @@ class Parser:
                 a.append(s)
             elif self.accept('colon'):
                 if not isinstance(s, IdNode):
-                    raise ParseException('Keyword argument must be a plain identifier.',
+                    raise ParseException('Dictionary key must be a plain identifier.',
                                          self.getline(), s.lineno, s.colno)
                 a.set_kwarg(s.value, self.statement())
                 potential = self.current
@@ -664,10 +707,17 @@ class Parser:
         t = self.current
         self.expect('id')
         varname = t
+        varnames = [t]
+
+        if self.accept('comma'):
+            t = self.current
+            self.expect('id')
+            varnames.append(t)
+
         self.expect('colon')
         items = self.statement()
         block = self.codeblock()
-        return ForeachClauseNode(varname.lineno, varname.colno, varname, items, block)
+        return ForeachClauseNode(varname.lineno, varname.colno, varnames, items, block)
 
     def ifblock(self):
         condition = self.statement()
diff --git a/run_unittests.py b/run_unittests.py
index 3608d3e..b581e12 100755
--- a/run_unittests.py
+++ b/run_unittests.py
@@ -2328,6 +2328,20 @@ class FailureTests(BasePlatformTests):
         self.assertEqual(cm.exception.returncode, 2)
         self.wipe()
 
+    def test_dict_requires_key_value_pairs(self):
+        self.assertMesonRaises("dict = {3, 'foo': 'bar'}",
+                               'Only key:value pairs are valid in dict construction.')
+        self.assertMesonRaises("{'foo': 'bar', 3}",
+                               'Only key:value pairs are valid in dict construction.')
+
+    def test_dict_forbids_duplicate_keys(self):
+        self.assertMesonRaises("dict = {'a': 41, 'a': 42}",
+                               'Duplicate dictionary key: a.*')
+
+    def test_dict_forbids_integer_key(self):
+        self.assertMesonRaises("dict = {3: 'foo'}",
+                               'Key must be a string.*')
+
 
 class WindowsTests(BasePlatformTests):
     '''
diff --git a/test cases/common/199 dict/meson.build b/test cases/common/199 dict/meson.build
new file mode 100644
index 0000000..e1ee2e3
--- /dev/null
+++ b/test cases/common/199 dict/meson.build
@@ -0,0 +1,23 @@
+project('dict test', 'c')
+
+dict = {'foo' : 'bar',
+        'baz' : 'foo',
+        'foo bar': 'baz'}
+
+exe = executable('prog', sources : ['prog.c'])
+
+i = 0
+
+foreach key, value : dict
+  test('dict test @0@'.format(key), exe,
+    args : [dict[key], value])
+  i += 1
+endforeach
+
+assert(i == 3, 'There should be three elements in that dictionary')
+
+empty_dict = {}
+
+foreach key, value : empty_dict
+  assert(false, 'This dict should be empty')
+endforeach
diff --git a/test cases/common/199 dict/prog.c b/test cases/common/199 dict/prog.c
new file mode 100644
index 0000000..bf0999d
--- /dev/null
+++ b/test cases/common/199 dict/prog.c
@@ -0,0 +1,8 @@
+#include <string.h>
+
+int main(int argc, char **argv) {
+  if (argc != 3)
+    return 1;
+
+  return strcmp(argv[1], argv[2]);
+}