Dictionary keys by variable do not store correctly

[jimbeauphloyd]

Godot version:
Godot Engine v4.0.dev.custom_buld.f97280a01

OS/device including version:
Mac OSX 10.15.5
Vulkan

Issue description:
Passing a variable key to a dictionary does not place values in the correct key.

Result:

{A:[A entry 0, B entry 1, A entry 2, B entry 3, A entry 4, B entry 5], B:[...]}

Expected Result:

{A:[A entry 0, A entry 1, A entry 2], B:[B entry 0, B entry 1, B entry 2]}

Steps to reproduce:

extends Node

var _entries = {}

func _ready():
	var key
	key = "A"
	_entries[key] = []
	key = "B"
	_entries[key] = []
	_add_entry("A")
	_add_entry("B")
	_add_entry("A")
	_add_entry("B")
	_add_entry("A")
	_add_entry("B")
	print(_entries)

func _add_entry(key):
	_entries[key].append(key + " entry " + str(_entries[key].size()))

Minimal reproduction project: DictionaryBug.zip

[EricEzaM]

Seems to be with the initialization of the values. This gives the expected output:

extends Node

var _entries = {}

func _ready():
	_entries = {
		"A": [],
		"B": []
	}
	_add_entry("A")
	_add_entry("B")
	_add_entry("A")
	_add_entry("B")
	_add_entry("A")
	_add_entry("B")
	print(_entries)

func _add_entry(key):
	_entries[key].append(key + " entry " + str(_entries[key].size()))

{A:[A entry 0, A entry 1, A entry 2], B:[B entry 0, B entry 1, B entry 2]}

[EricEzaM]

Additionally, expanding this to:

	_entries = {
		"A": [],
		"B": []
	}
	_entries["C"] = []
	var key = "D"
	_entries[key] = []
	_add_entry("A")
	_add_entry("B")
	_add_entry("A")
	_add_entry("B")
	_add_entry("A")
	_add_entry("B")
	_add_entry("C")
	_add_entry("D")
	_add_entry("C")
	_add_entry("D")
	_add_entry("A")
	_add_entry("B")
	_add_entry("A")
	_add_entry("B")
	print(_entries["A"]) # [A entry 0, A entry 1, A entry 2, A entry 3, A entry 4]
	print(_entries["B"]) # [B entry 0, B entry 1, B entry 2, B entry 3, B entry 4]
	print(_entries["C"]) # [C entry 0, D entry 1, C entry 2, D entry 3]
	print(_entries["D"]) # [C entry 0, D entry 1, C entry 2, D entry 3]

"A" and "B" remain correct, but "C" and "D" get mixed up. However, they do not get values from "A" and "B" even when values are added to A and B after C and D.

[sednave]

Initializing each array with UNIQUE values seems to give the expected output, but only if it's unique. Otherwise, Godot writes to the same array, e.g.

	var key
	key = "A"
	_entries[key] = [1]
	key = "B"
	_entries[key] = [2]
	key = "C"
	_entries[key] = [2] # Same as B
	var new_array = [2] # Standalone variable, not in dictionary, same as B
	_add_entry("A")
	_add_entry("B")
	_add_entry("A")
	_add_entry("B")
	_add_entry("A")
	_add_entry("B")
	_add_entry("C")
	_add_entry("C")
	_add_entry("C")
	print(_entries["A"]) # [1, A entry 1, A entry 2, A entry 3]
	print(_entries["B"]) # [2, B entry 1, B entry 2, B entry 3, C entry 4, C entry 5, C entry 6]
	print(_entries["C"]) # [2, B entry 1, B entry 2, B entry 3, C entry 4, C entry 5, C entry 6]
	print(new_array) # [2, B entry 1, B entry 2, B entry 3, C entry 4, C entry 5, C entry 6]

"A" points to a unique array, but "B" and "C" appear to reference the same array.

Additionally: If you set _entries["A"][0] = 2 so that it looks like "B" and "C" = [2], "A" is still unique and gives output: [2, A entry 1, A entry 2, A entry 3]

So the problem only seems to occur when you use the '=' operator to assign an array that's been initialized the same as another array to a variable.

[ThakeeNathees]

A simplified version of the issue

func _ready():
	var v1 = []
	var v2 = []  ## both arrays are reduced to Array const and shares the same memory in constant map.
	
	v1.append(42)
	print(v2)   ## prints [42]

In 3.2 the literal array doesn't reduced to variant (even if all elements are compile time const) but it was ArrayNode and constructed at runtime (OPCODE_CONSTRUCT_ARRAY) but in 4.0 it's reduced to Array constant at GDScriptAnalyzer::reduce_array() and since it's a constant value every other similar array will points to the same location in the local constant map.

similar issue : #20436

adding constant to constant_map first search if it already exists, is it okey to ignore that existence search for arrays/ and dictionaries @vnen ?

[vnen]

adding constant to constant_map first search if it already exists, is it okey to ignore that existence search for arrays/ and dictionaries

Yeah, I was thinking about that. Though I'm not sure if we actually want to keep arrays/dictionaries in the constant map. It is theoretically faster (since it doesn't need to be built at runtime) but the space needed might not be worth it.