Fix extended assign with @ and & syntax

Fixes robotframework#5405.

Author: pekkaklarck

atest/robot/variables/extended_assign.robot

@@ -20,6 +20,12 @@ Set item to list attribute
 Set item to dict attribute
     Check Test Case    ${TESTNAME}
 
+Set using @-syntax
+    Check Test Case    ${TESTNAME}
+
+Set using &-syntax
+    Check Test Case    ${TESTNAME}
+
 Trying to set un-settable attribute
     Check Test Case    ${TESTNAME}
 
@@ -37,6 +43,3 @@ Strings and integers do not support extended assign
 
 Attribute name must be valid
     Check Test Case    ${TESTNAME}
-
-Extended syntax is ignored with list variables
-    Check Test Case    ${TESTNAME}

atest/testdata/variables/extended_assign.robot

@@ -2,6 +2,9 @@
 Variables    extended_assign_vars.py
 Library      Collections
 
+*** Variables ***
+&{DICT}      key=value
+
 *** Test Cases ***
 Set attributes to Python object
     [Setup]    Should Be Equal    ${VAR.attr}-${VAR.attr2}    value-v2
@@ -25,31 +28,47 @@ Set item to list attribute
     ${body.data}[${0}] =     Set Variable    firstVal
     ${body.data}[-1] =       Set Variable    lastVal
     ${body.data}[1:3] =      Create List     ${98}        middle    ${99}
-    ${EXPECTED_LIST} =       Create List     firstVal     ${98}     middle    ${99}     lastVal
-    Lists Should Be Equal    ${body.data}    ${EXPECTED_LIST}
+    Lists Should Be Equal    ${body.data}    ${{['firstVal', 98, 'middle', 99, 'lastVal']}}
 
 Set item to dict attribute
     &{body} =                        Evaluate              {'data': {'key': 'val', 0: 1}}
     ${body.data}[key] =              Set Variable          newVal
     ${body.data}[${0}] =             Set Variable          ${2}
     ${body.data}[newKey] =           Set Variable          newKeyVal
-    ${EXPECTED_DICT} =               Create Dictionary     key=newVal    ${0}=${2}    newKey=newKeyVal
-    Dictionaries Should Be Equal     ${body.data}          ${EXPECTED_DICT}
+    Dictionaries Should Be Equal     ${body.data}          ${{{'key': 'newVal', 0: 2, 'newKey': 'newKeyVal'}}}
+
+Set using @-syntax
+    [Documentation]    FAIL Setting '\@{VAR.fail}' failed: Expected list-like value, got string.
+    @{DICT.key} =    Create List    1    2    3
+    Should Be Equal    ${DICT}    ${{{'key': ['1', '2', '3']}}}
+    @{VAR.list: int} =    Create List    1    2    3
+    Should Be Equal    ${VAR.list}    ${{[1, 2, 3]}}
+    @{VAR.fail} =    Set Variable    not a list
+
+Set using &-syntax
+    [Documentation]    FAIL Setting '\&{DICT.fail}' failed: Expected dictionary-like value, got integer.
+    &{VAR.dict} =    Create Dictionary    key=value
+    Should Be Equal    ${VAR.dict}    ${{{'key': 'value'}}}
+    Should Be Equal    ${VAR.dict.key}    value
+    &{DICT.key: int=float} =    Create Dictionary    1=2.3    ${4.0}=${5.6}
+    Should Be Equal    ${DICT}    ${{{'key': {1: 2.3, 4: 5.6}}}}
+    Should Be Equal    ${DICT.key}[${1}]    ${2.3}
+    &{DICT.fail} =    Set Variable    ${666}
 
 Trying to set un-settable attribute
-    [Documentation]    FAIL STARTS: Setting attribute 'not_settable' to variable '\${VAR}' failed: AttributeError:
+    [Documentation]    FAIL STARTS: Setting '\${VAR.not_settable}' failed: AttributeError:
     ${VAR.not_settable} =    Set Variable    whatever
 
 Un-settable attribute error is catchable
     [Documentation]    FAIL GLOB:
     ...    Teardown failed:
     ...    Several failures occurred:
     ...
-    ...    1) Setting attribute 'not_settable' to variable '\${VAR}' failed: AttributeError: *
+    ...    1) Setting '\${VAR.not_settable}' failed: AttributeError: *
     ...
     ...    2) AssertionError
     Run Keyword And Expect Error
-    ...    Setting attribute 'not_settable' to variable '\${VAR}' failed: AttributeError: *
+    ...    Setting '\${VAR.not_settable}' failed: AttributeError: *
     ...    Setting unsettable attribute
     [Teardown]    Run Keywords    Setting unsettable attribute    Fail
 
@@ -78,11 +97,6 @@ Attribute name must be valid
     Should Be Equal    ${VAR.2nd}    starts with number
     Should Be Equal    ${VAR.foo-bar}    invalid char
 
-Extended syntax is ignored with list variables
-    @{list} =    Create List    1    2    3
-    @{list.new} =    Create List    1    2    3
-    Should Be Equal    ${list}    ${list.new}
-
 *** Keywords ***
 Extended assignment is disabled
     [Arguments]   ${value}

src/robot/variables/assigner.py

@@ -123,7 +123,7 @@ def assign(self, return_value):
             context.info(format_assign_message(name, value, items))
 
     def _extended_assign(self, name, value, variables):
-        if name[0] != "$" or "." not in name or name in variables:
+        if "." not in name or name in variables:
             return False
         base, attr = [token.strip() for token in name[2:-1].rsplit(".", 1)]
         try:
@@ -136,12 +136,9 @@ def _extended_assign(self, name, value, variables):
         ):
             return False
         try:
-            setattr(var, attr, value)
+            setattr(var, attr, self._handle_list_and_dict(value, name[0]))
         except Exception:
-            raise VariableError(
-                f"Setting attribute '{attr}' to variable '${{{base}}}' failed: "
-                f"{get_error_message()}"
-            )
+            raise VariableError(f"Setting '{name}' failed: {get_error_message()}")
         return True
 
     def _variable_supports_extended_assign(self, var):
@@ -168,12 +165,12 @@ def _raise_cannot_set_type(self, value, expected):
         value_type = type_name(value)
         raise VariableError(f"Expected {expected}-like value, got {value_type}.")
 
-    def _validate_item_assign(self, name, value):
-        if name[0] == "@":
+    def _handle_list_and_dict(self, value, identifier):
+        if identifier == "@":
             if not is_list_like(value):
                 self._raise_cannot_set_type(value, "list")
             value = list(value)
-        if name[0] == "&":
+        if identifier == "&":
             if not is_dict_like(value):
                 self._raise_cannot_set_type(value, "dictionary")
             value = DotDict(value)
@@ -195,8 +192,7 @@ def _item_assign(self, name, items, value, variables):
             except ValueError:
                 pass
         try:
-            value = self._validate_item_assign(name, value)
-            var[selector] = value
+            var[selector] = self._handle_list_and_dict(value, name[0])
         except (IndexError, TypeError, Exception):
             raise VariableError(
                 f"Setting value to {type_name(var)} variable "