Enforce displaying Amount with trailing zeros

[448-OG]

It is common to display bitcoins using trailing zeros upto 8 decimals. This commit enforces:

• Displaying Amount in BTC with trailing zeroes by eight decimal places if a precision on the Amount is not specified.
• Displaying Amount in BTC upto the precision specified truncating the insignificant zeros.
• Displaying amount in BTC without any decimals if the remainder of the amount divided by the satoshis in 1 BTC is equal to zero using formula satoshis.rem_euclid(Amount::ONE_BTC.to_sat()) != 0

These are not breaking changes and all previous tests pass.

A testcase is added to for changes introduced.

Resolves: #2136

[coveralls]

Pull Request Test Coverage Report for Build 8316149718

Details

• 37 of 37 (100.0%) changed or added relevant lines in 1 file are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.02%) to 83.927%

---

Totals
Change from base Build 8307227520:	0.02%
Covered Lines:	19732
Relevant Lines:	23511

---

💛 - Coveralls

[apoelstra]

The CI failure is real -- you're introducing a dependence on alloc in the fmt method that didn't used to be there.

In principle we shouldn't need one.

Interestingly my local CI passes -- so we've found a blind spot in it! Let me investigate..

[apoelstra]

Oh, lol, the blind spot is the entire units crate. Oops. This may also explain another "how did this get past CI?" situation last week..

[sanket1729]

I forgot what our consensus was about respecting FromStr and Display invariant? Do we make an effort to maintain it?

[448-OG]

The CI failure is real -- you're introducing a dependence on alloc in the fmt method that didn't used to be there.

In principle we shouldn't need one.

Interestingly my local CI passes -- so we've found a blind spot in it! Let me investigate..

Yeah! Realized it was an issue with allocation but I was not able to make changes yesterday. Should be fixed now.

My tests also passed locally. Not sure why

[448-OG]

What is the current policy on running rustfmt, my editor does auto format but when I do a diff I see so many changes related to formatting

[448-OG]

So I also need to fix it for tests, somehow they succeed locally

[apoelstra]

What is the current policy on running rustfmt, my editor does auto format but when I do a diff I see so many changes related to formatting

Please do not commit unrelated changes. Usually there should not be very many because we have a weekly bot which does all the formatting changes, but lately we have been skipping the bot because one mantainer claims undue difficulty in rebasing.

So you will need to override your editor or be careful about what changes you commit, for now.

[apoelstra]

I forgot what our consensus was about respecting FromStr and Display invariant? Do we make an effort to maintain it?

Yes, we "make an effort". But there are some exceptional cases, most notably Script, and I don't think we've worked out an explicit policy.

[sanket1729]

@448-OG, you can use just format that would internally use the nightly formatter. In your editor is vscode, you can configure project specific settings for rust-bitcoin and set the formatter as just format

[sanket1729]

ACK d887423

[apoelstra]

ACK d887423