Create a pre call hook onBeforeExecTransaction

[akshay-ap]

Fixes #775, #735

To have a broader context on overall changes in the code use this diff

Changes in PR:

• Add a pre-hook function onBeforeExecTransaction
• Refactor changes in #772, #774
• Add a pre-hook function onBeforeExecTransactionFromModule
• Change function visibility of execTransaction from public to external

Code size change

Increase by 51 bytes in Safe with diff: https://github.com/safe-global/safe-smart-account/compare/499b17ad..improvement-execTransaction-post-call-hook:

This PR

Safe 21832 bytes (limit is 24576)
SafeL2 22612 bytes (limit is 24576)

Commit (Prior to merging #772)

Safe 21781 bytes (limit is 24576)
SafeL2 22623 bytes (limit is 24576)

Gas usage with Safe contract

• Increase by 79 gas in execTransaction calls
• Increase by 44 gas in execTransactionFromModule* calls

This PR

·------------------------------------------------------------|----------------------------|-------------|------------------------------·
|                    Solc version: 0.7.6                     ·  Optimizer enabled: false  ·  Runs: 200  ·  Block limit: 100000000 gas  │
·····························································|····························|·············|·······························
|  Methods                                                                                                                             │
·····················|·······································|·············|··············|·············|···············|···············
|  Contract          ·  Method                               ·  Min        ·  Max         ·  Avg        ·  # calls      ·  usd (avg)   │
·····················|·······································|·············|··············|·············|···············|···············
|  Safe              ·  execTransaction                      ·      51999  ·     3638489  ·     133046  ·          248  ·           -  │
·····················|·······································|·············|··············|·············|···············|···············
|  Safe              ·  execTransactionFromModule            ·      51625  ·      184218  ·     127860  ·           11  ·           -  │
·····················|·······································|·············|··············|·············|···············|···············
|  Safe              ·  execTransactionFromModuleReturnData  ·      52268  ·      183974  ·     107914  ·            5  ·           -  │
·····················|·······································|·············|··············|·············|···············|···············

Commit (Prior to merging #772)

·------------------------------------------------------------|----------------------------|-------------|------------------------------·
|                    Solc version: 0.7.6                     ·  Optimizer enabled: false  ·  Runs: 200  ·  Block limit: 100000000 gas  │
·····························································|····························|·············|·······························
|  Methods                                                                                                                             │
·····················|·······································|·············|··············|·············|···············|···············
|  Contract          ·  Method                               ·  Min        ·  Max         ·  Avg        ·  # calls      ·  usd (avg)   │
·····················|·······································|·············|··············|·············|···············|···············
|  Safe              ·  execTransaction                      ·      51920  ·     3638410  ·     132980  ·          248  ·           -  │
·····················|·······································|·············|··············|·············|···············|···············
|  Safe              ·  execTransactionFromModule            ·      51581  ·      184186  ·     127818  ·           11  ·           -  │
·····················|·······································|·············|··············|·············|···············|···············
|  Safe              ·  execTransactionFromModuleReturnData  ·      52224  ·      183930  ·     107870  ·            5  ·           -  │
·····················|·······································|·············|··············|·············|···············|···············

Alternatives considered

A.

Add a post call hook onAfterExecTransaction

Cons:

• If a transaction updates threshold of a Safe, then event emits new threshold rather than emitting the value prior to the update. I tried adding additionalInfo as a method parameter and building this value prior to the execution but compiler reports CompilerError: Stack too deep, try removing local variables.
• Changes order of emitted events.

[coveralls]

Pull Request Test Coverage Report for Build 9677986904

Details

• 2 of 2 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 92.909%

---

Totals
Change from base Build 9676758763:	0.0%
Covered Lines:	389
Relevant Lines:	401

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 9693321609

Details

• 1 of 2 (50.0%) changed or added relevant lines in 2 files are covered.
• 4 unchanged lines in 1 file lost coverage.
• Overall coverage decreased (-0.7%) to 92.185%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
contracts/SafeL2.sol	0	1	0.0%
<!--	Total:	1	2	50.0%	-->

Files with Coverage Reduction	New Missed Lines	%
contracts/SafeL2.sol	4	0.0%
<!--	Total:	4		-->

Totals
Change from base Build 9676758763:	-0.7%
Covered Lines:	384
Relevant Lines:	401

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 9694147162

Details

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 92.909%

---

Totals
Change from base Build 9676758763:	0.0%
Covered Lines:	389
Relevant Lines:	401

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 9694187165

Details

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 92.909%

---

Totals
Change from base Build 9676758763:	0.0%
Covered Lines:	389
Relevant Lines:	401

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 9694410087

Details

• 3 of 3 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 92.909%

---

Totals
Change from base Build 9676758763:	0.0%
Covered Lines:	389
Relevant Lines:	401

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 9695364178

Details

• 3 of 3 (100.0%) changed or added relevant lines in 2 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage remained the same at 92.909%

---

Files with Coverage Reduction	New Missed Lines	%
contracts/base/ModuleManager.sol	1	92.93%
<!--	Total:	1		-->

Totals
Change from base Build 9676758763:	0.0%
Covered Lines:	389
Relevant Lines:	401

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 9695778501

Details

• 3 of 3 (100.0%) changed or added relevant lines in 2 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage remained the same at 92.909%

---

Files with Coverage Reduction	New Missed Lines	%
contracts/base/ModuleManager.sol	1	92.93%
<!--	Total:	1		-->

Totals
Change from base Build 9676758763:	0.0%
Covered Lines:	389
Relevant Lines:	401

---

💛 - Coveralls

[coveralls]

Pull Request Test Coverage Report for Build 9696059645

Details

• 2 of 2 (100.0%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.01%) to 92.899%

---

Totals
Change from base Build 9676758763:	-0.01%
Covered Lines:	388
Relevant Lines:	400

---

💛 - Coveralls