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cmd/achdiff: Tool for comparing ACH files
What were you trying to do?
When debugging an ACH file we created in parallel to one created by an existing solution we will need to spot differences in the two files to fix bugs in our code or configuration.
What did you expect to see?
I could see a tool like the following:
$ achdiff theirs.ach ours.ach
Header:
FileCreationTime: 1231 vs 1421
Batches:
#1:
CompanyDiscretionaryData:
Theirs: Foo
Ours: Bar
Thoughts?
Edit 2019-09-17:
Adam: my primary usecase for this is to diff files created by paygate and the customer’s existing solution
Yep we can see the fallout, clean up and move forward! Legacy has been out there for many years so it should be stable just in a language that sales and marketing considers antiquated. I imagine every bank is running some core version of legacy ach code. With the longevity of the ach specification, there should have been no reason for FI customization.
In short we should be able to compare, troubleshoot, and fix! Great stuff Adam.
One challenge would be accessing the code from an existing solution. Moov code is accessible by all.
I'm not thinking about the code that we're running in parallel with, but the raw files they're producing. I imagine we're going to get files from the existing code to compare against files we create (for the same transfer sent through both).
We talked about this a lot today. There are a few experiments we should run regarding how the files are displayed in a "human readable" format. Use the horizontal or vertical space to arrange fields next to each other (useful for diffs) along with color.
Some ideas:
Describing ACH file 'test/testdata/ppd-debit.ach' Describing ACH file 'test/testdata/ppd-debit.ach'
Origin OriginName Destination DestinationName Origin OriginName Destination DestinationName
121042882 My Bank Name 231380104 Federal Reserve Bank 121042882 My Bank Name 231380104 Federal Reserve Bank
BatchNumber Type ServiceClass Addendas TotalDebits TotalCredits BatchNumber Type ServiceClass Addendas TotalDebits TotalCredits
1 PPD 225 1 100000000 0 1 PPD 225 1 100000000 0
TxCode AccountNumber Amount Name TraceNumber TxCode AccountNumber Amount Name TraceNumber
27 12345678 100000000 Receiver Account Name 121042880000001 27 12345678 100000000 Other Name 121042880000001
Describing ACH file 'test/testdata/ppd-debit.ach'
Origin OriginName Destination DestinationName
121042882 My Bank Name 231380104 Federal Reserve Bank
BatchNumber Type ServiceClass Addendas TotalDebits TotalCredits
1 PPD 225 1 100000000 0
TxCode AccountNumber Amount Name TraceNumber
- 27 12345678 100000000 Receiver Account Name 121042880000001
+ 27 12345678 100000000 Other Name 121042880000001
Overall, let's organize the information so our brains pick them up the best. That means diff'd data is close to each other and color coded (along with + / -, or similar, markers).
Also, there are industry formats we might adopt as well (for input/output)
https://www.frbservices.org/financial-services/ach/fedpayments-reporter/report-descriptions.html
That's right Wade provided that.
To diff two ACH files let's require -diff as a CLI flag and otherwise just show multiple files one after the other.
In the future I can see supporting flags like -merge / -flatten, -sort (for Batches or EntryDetail's across files) to help optimize and organize file contents.
The initial concept was based on this.
$ achdiff theirs.ach ours.ach Header: FileCreationTime: 1231 vs 1421
I've lumped this into https://github.com/moov-io/ach/pull/622 and will figure out colorization (it doesn't work in my default macOS terminal for some reason..)