Conds can produce syntax errors

[rodionovv]

fixes #172

Everything discussed in #172 is added.

But i mentioned that solution discussed in #172 is not working for all cases. Checking the size of bytes to be written is working only when all input strings are empty. But if some of them are empty and some are not syntax errors will still be produced. So case like this:

sb.And("", "1 = 1", "")

will produce this sql string:

( AND 1 = 1 AND )

Since total length of input is not zero everything will be inserted. The best way to fix this issue i found is to edit WriteStrings function. It checks for the size of strings its writing to buffer and if it's empty it skips the step also ignoring separator.

Also i added validation of strings in all Conds where string argument is present. All of them might produce syntax errors if string is empty. For example EQ will produce string like: = 1 if field is empty.

[coveralls]

coverage: 96.84% (+0.3%) from 96.582%
when pulling 961c268 on rodionovv:string-validation
into c329655 on huandu:master.

[huandu]

Need some cases to cover this branch.

[rodionovv]

I've added test covering those lines. But found another problem.

Now building with WHERE clause can produce an extra blank space. In case WHERE was added through AddWhereExpr function. Since it can be only applied to an existing and non nil WhereClause it will be replaced with empty space during Build stage.

This problem can be reproduced for both empty array and array of empty strings. I've added two test cases TestEmptyStringsWhereAddWhereExpr and TestEmptyAddWhereExpr to demonstrate how it can be achieved. They have empty spaces at the end of expected results strings so they will pass.

I felt that fixing this is not a part of current pr. I think its a bit another problem rather the one i was trying to fix here. I can still try to fix it in a current or maybe in a new pr. What do you think about it?

[huandu]

Thanks for your contribution!

Your PR looks good to me in general. Just one comment: You can add some cases to test against the empty WHERE clause case, e.g. Select("*").From("a").Where("", "") should build SELECT * FROM a.

[huandu]

LGTM

[huandu]

Released in tag v1.31.0.