Do something meaningful with SQL exceptions

[jaragunde]

Certain DAO operations may throw SQL exceptions, one example is PostgreSQLTaskDAO::create(), which may throw SQLUniqueViolationException or SQLQueryErrorException. We currently let them flow up in the code, eventually crashing and resulting in an internal server error and a HTTP status 500 in the response.

We should do something with these exceptions and make the backend fail gracefully, returning a meaningful error message. I think the DAO layer can still throw these exceptions, but the business logic layer (Facade/Action classes) should catch them and act in consequence.

This is the cause of some reported errors, like #492 and #495. It's very related with #173, too.

[jaragunde]

This is also the root cause behind #110 and #175.

[jaragunde]

We don't have a good way in the business logic layer (facades & actions) to pass detailed information to the upper layer in case of error. I would create an OperationResult class that would be returned by CRUD operations in the business logic layer. This class would have a boolean success field, and fields for an error number and message. It could even contain a list of tasks, the ones that we failed to create/update/delete.

Then, web services would check the OperationResult and return the information in it in case of error.

[jaragunde]

Danielle started working on this problem and I've been following up. Some fixes have been merged lately.

From PR #608:

a968bd17 Merge pull request #608 from Igalia/bubble-up-sql-errors [Danielle M]
7ec2b2fe Fix string construction in service [Danielle Mayabb]
207ea879 (origin/bubble-up-sql-errors) Clean up formatting, use getters [Danielle Mayabb]
5bfa360e Clean up some xml so that messages are returned correctly [Danielle Mayabb]
a4175f5b Fix formatting/naming, return error code on error [Danielle Mayabb]
cfcdc447 Reload data store if creation fails [Danielle Mayabb]
a15d8cae Update save of dates, facade, and service [Danielle Mayabb]
d1940ea5 Add error handling for not null violation [Danielle Mayabb]
7762bffd Update object metadata and fix date conversion [Danielle Mayabb]
b9d4be4a Update copyright and remove trailing whitespace [Danielle Mayabb]
6c080269 Update var convention and delete whitespace [Danielle Mayabb]
90337f62 Expand exception handling in projectManagement.js [Danielle Mayabb]
6ad9871c Update createProjectsService to check new property isSuccessful [Danielle Mayabb]
074632f4 Update Project action, facade, and DAO [Danielle Mayabb]
d58e254f Update ProjectDAO create to use PDO and return OperationResult [Danielle Mayabb]
441c31a4 Add OperationResult class [Danielle Mayabb]

From PR #614:

f0ae97d8 Delete unused test code. [Jacobo Aragunde Pérez]
3145b3b3 [#172] Delete user assignment when deleting a project. [Jacobo Aragunde Pérez]
55d87e67 [#496,#513] Return more specific errors on project deletion. [Jacobo Aragunde Pérez]
1b1aa84c Remove unused constructor for ProjectDAO. [Jacobo Aragunde Pérez]

[jaragunde]

Merged in #616:

f3f8c5f3 [#492, #496] Manage and return SQL errors on task creation. [Jacobo Aragunde Pérez]
00088a42 [#173] Allow to report multiple errors on the same creation batch. [Jacobo Aragunde Pérez]
f4700807 [#173] Report several kinds of errors on task creation. [Jacobo Aragunde Pérez]
a2a96ce8 Prevent calling task create without overlap check. [Jacobo Aragunde Pérez]

[jaragunde]

Merged in #615:

0aeaf6e6 [#496, #513] Replace project partial update operation. [Jacobo Aragunde Pérez]
3fe93733 [#496,#513] Return more specific errors on project update. [Jacobo Aragunde Pérez]
b7b339bd Simplify project create operation. [Jacobo Aragunde Pérez]

[jaragunde]

Merged in #618:

82d4d972 [#496] Review error response codes in task operations. [Jacobo Aragunde Pérez]
ddbeb195 [#173] Make error messages more noticeable. [Jacobo Aragunde Pérez]
13e9c2b2 [#496,#513] Return more detailed errors on task delete. [Jacobo Aragunde Pérez]
e49f20e5 [#496] Return more detailed errors on task update. [Jacobo Aragunde Pérez]

[jaragunde]

Merged in PR #621:

04cc1fdb [#173,#496] Report better errors on user CRUD operations [Jacobo Aragunde Pérez]
e0fd7893 [#173] Report warning message from LDAP backend to users. [Jacobo Aragunde Pérez]
73b21e5f [#173,#496] Report detailed errors on user delete. [Jacobo Aragunde Pérez]
d9b60724 [#173,#496] Report better errors from LDAP user update DAO. [Jacobo Aragunde Pérez]
999ec3f3 [#173,#496] Report detailed errors on user update. [Jacobo Aragunde Pérez]
0708ec42 [#173,#496] Report better errors from LDAP user create DAO. [Jacobo Aragunde Pérez]
2ea7e95f [#173,#496] Report detailed errors on user creation. [Jacobo Aragunde Pérez]
4d307f27 [#431] Fix calling sizeof on non-countable. [Jacobo Aragunde Pérez]