Fix AutoMigrate default value comparison for string fields (issue #7590)

[nowindexman]

bugfix:AutoMigrate #7590

[propel-code-bot]

Fix AutoMigrate Default Value Comparison for String Fields

This pull request addresses issue #7590 by refining how AutoMigrate determines whether a column should be altered when comparing string-type default values. The update introduces special logic for string fields to handle discrepancies caused by surrounding quotes, ensuring that unnecessary column alterations are avoided if only quotation differences exist. The solution introduces a check that leverages strings.Trim(field.DefaultValue, "'\"") for more accurate comparison, following reviewer feedback.

Key Changes

• Added a case schema.String branch to the default value comparison logic in migrator/migrator.go.
• Comparison now ensures that a column is only flagged for alteration if the existing default value differs from both the raw and trimmed (quotes removed) forms of the schema default.
• Utilized strings.Trim(field.DefaultValue, "'\"") to eliminate discrepancies due solely to surrounding quotes.
• No other functionality outside default value comparison is affected.

Affected Areas

• migrator/migrator.go - logic within the MigrateColumn function as part of the type/default value comparison flow

This summary was automatically generated by @propel-code-bot

[propel-code-bot]

[CriticalError]

Logic error in string default value comparison: The condition dv != field.DefaultValue || dv != strings.Trim(field.DefaultValue, "'") will always evaluate to true because of the OR operator. If dv == field.DefaultValue, then dv != strings.Trim(field.DefaultValue, "'") will likely be true (unless the field value has quotes). This means alterColumn will always be set to true for string fields, causing unnecessary column alterations.

The logic should use AND operator to check if the values are different in both forms:

Suggested change

	case schema.String:
	if dv != field.DefaultValue || dv != strings.Trim(field.DefaultValue, "'") {
	alterColumn = true
	}
	case schema.String:
	if dv != field.DefaultValue && dv != strings.Trim(field.DefaultValue, "'") {
	alterColumn = true
	}

⚡ Committable suggestion

Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation.

Context for Agents

[**CriticalError**]

Logic error in string default value comparison: The condition `dv != field.DefaultValue || dv != strings.Trim(field.DefaultValue, "'")` will always evaluate to `true` because of the OR operator. If `dv == field.DefaultValue`, then `dv != strings.Trim(field.DefaultValue, "'")` will likely be true (unless the field value has quotes). This means `alterColumn` will always be set to `true` for string fields, causing unnecessary column alterations.

The logic should use AND operator to check if the values are different in both forms:

```suggestion
			case schema.String:
				if dv != field.DefaultValue && dv != strings.Trim(field.DefaultValue, "'") {
					alterColumn = true
				}
```

⚡ **Committable suggestion**

Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation.

File: migrator/migrator.go
Line: 566

[jinzhu]

change to strings.Trim(field.DefaultValue, "'\"")?

[nowindexman]

Got it, already updated.

[nowindexman]

@jinzhu Can this be merged into the main branch?