Fix normalization of custom array type

[isaacparker0]

Fix custom type arrays (enums, composites, domains) incorrectly outputting PostgreSQL's internal _typename format instead of SQL standard typename[] syntax.

[Copilot]

Pull Request Overview

This PR fixes the normalization of custom array types (enums, composites, domains) by converting PostgreSQL's internal _typename format to the SQL standard typename[] syntax. This ensures that DDL statements and schema comparisons use the correct array notation.

Key changes:

• Added logic to detect and convert underscore-prefixed custom array types to bracket notation
• Added test case for enum array columns to verify the fix

Reviewed Changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
ir/normalize.go	Added custom array type normalization logic to convert _typename to typename[] format
testdata/diff/create_table/enum_array_column/old.sql	Test fixture: schema before adding enum array column
testdata/diff/create_table/enum_array_column/new.sql	Test fixture: schema after adding enum array column
testdata/diff/create_table/enum_array_column/diff.sql	Expected DDL output showing status[] array syntax
testdata/diff/create_table/enum_array_column/plan.sql	Expected plan SQL with normalized array type
testdata/diff/create_table/enum_array_column/plan.txt	Human-readable plan output
testdata/diff/create_table/enum_array_column/plan.json	Machine-readable plan output in JSON format

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[Copilot]

The custom array type normalization only handles direct type names but doesn't handle type casts. When custom array types appear in expressions with type casts (e.g., value::_my_enum), they won't be normalized to value::my_enum[].

Consider adding normalization for custom array types in the type cast handling section (lines 756-759). For example:

// Replace PostgreSQL internal type names with standard SQL types in type casts
for pgType, sqlType := range typeMap {
    expr = strings.ReplaceAll(expr, "::"+pgType, "::"+sqlType)
}

// Handle custom array types in type casts
// e.g., ::_my_enum -> ::my_enum[]
expr = regexp.MustCompile(`::(pg_catalog\.)?_(\w+)`).ReplaceAllString(expr, "::$2[]")

[Copilot]

The pg_catalog prefix removal returns immediately without checking if the result is a custom array type. For example, pg_catalog._my_enum would be returned as _my_enum instead of being further normalized to my_enum[].

The logic should continue to check for the underscore prefix after removing pg_catalog:

// Remove pg_catalog prefix for unmapped types
if after, found := strings.CutPrefix(typeName, "pg_catalog."); found {
    typeName = after
}

// Handle custom array types (internal PostgreSQL array notation)
// e.g., _my_enum_type -> my_enum_type[]
if strings.HasPrefix(typeName, "_") {
    return typeName[1:] + "[]"
}

return typeName

Suggested change

	return after
	typeName = after

[tianzhou]

Good catch.

LGTM overall. I will merge this and make some refinement in a followup PR.

[tianzhou]

Followup #164