implement literal stringification for arrays

as we already implement stringification for the contents,
provide a bracketed syntax for default and ARRAY literal
for PG specifically.   ARRAY literal seems much simpler to
render than their quoted syntax which requires double quotes
for strings.

also open up testing for pg8000 which has likely been
fine with arrays for awhile now, bump the version pin
also.

Fixes: #8138
Change-Id: Id85b052b0a9564d6aa1489160e58b7359f130fdd

1 files changed, 20 insertions, 31 deletions

diff --git a/lib/sqlalchemy/dialects/postgresql/array.py b/lib/sqlalchemy/dialects/postgresql/array.py
index 3b5eaed30..515eb2d15 100644
--- a/lib/sqlalchemy/dialects/postgresql/array.py
+++ b/lib/sqlalchemy/dialects/postgresql/array.py
@@ -310,35 +310,6 @@ class ARRAY(sqltypes.ARRAY):
     def compare_values(self, x, y):
         return x == y
 
-    def _proc_array(self, arr, itemproc, dim, collection):
-        if dim is None:
-            arr = list(arr)
-        if (
-            dim == 1
-            or dim is None
-            and (
-                # this has to be (list, tuple), or at least
-                # not hasattr('__iter__'), since Py3K strings
-                # etc. have __iter__
-                not arr
-                or not isinstance(arr[0], (list, tuple))
-            )
-        ):
-            if itemproc:
-                return collection(itemproc(x) for x in arr)
-            else:
-                return collection(arr)
-        else:
-            return collection(
-                self._proc_array(
-                    x,
-                    itemproc,
-                    dim - 1 if dim is not None else None,
-                    collection,
-                )
-                for x in arr
-            )
-
     @util.memoized_property
     def _against_native_enum(self):
         return (
@@ -346,6 +317,24 @@ class ARRAY(sqltypes.ARRAY):
             and self.item_type.native_enum
         )
 
+    def literal_processor(self, dialect):
+        item_proc = self.item_type.dialect_impl(dialect).literal_processor(
+            dialect
+        )
+        if item_proc is None:
+            return None
+
+        def to_str(elements):
+            return f"ARRAY[{', '.join(elements)}]"
+
+        def process(value):
+            inner = self._apply_item_processor(
+                value, item_proc, self.dimensions, to_str
+            )
+            return inner
+
+        return process
+
     def bind_processor(self, dialect):
         item_proc = self.item_type.dialect_impl(dialect).bind_processor(
             dialect
@@ -355,7 +344,7 @@ class ARRAY(sqltypes.ARRAY):
             if value is None:
                 return value
             else:
-                return self._proc_array(
+                return self._apply_item_processor(
                     value, item_proc, self.dimensions, list
                 )
 
@@ -370,7 +359,7 @@ class ARRAY(sqltypes.ARRAY):
             if value is None:
                 return value
             else:
-                return self._proc_array(
+                return self._apply_item_processor(
                     value,
                     item_proc,
                     self.dimensions,