clippy: ledger-tool lints

[steviez]

Problem

There are new nightly clippy lints in the ledger-tool source. See the parent issue #34626 for more context

Summary of Changes

Apply the change suggested below

warning: `flatten()` will run forever if the iterator repeatedly produces an `Err`
    --> ledger-tool/src/main.rs:2649:39
     |
2649 |                 for line in f.lines().flatten() {
     |                                       ^^^^^^^^^ help: replace with: `map_while(Result::ok)`
     |
note: this expression returning a `std::io::Lines` may produce an infinite number of `Err` in case of a read error
    --> ledger-tool/src/main.rs:2649:29
     |
2649 |                 for line in f.lines().flatten() {
     |                             ^^^^^^^^^
     = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#lines_filter_map_ok
     = note: `#[warn(clippy::lines_filter_map_ok)]` on by default

warning: `solana-ledger-tool` (bin "solana-ledger-tool" test) generated 1 warning

[brooksprumo]

Looks good to me. Can you confirm this still works as intended? (I wasn't familiar with the lines() stuff, which is why I didn't do this one myself heh.)

[codecov]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (d6146af) 81.8% compared to head (212937e) 81.8%.
Report is 8 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master   #34640   +/-   ##
=======================================
  Coverage    81.8%    81.8%           
=======================================
  Files         824      824           
  Lines      222262   222257    -5     
=======================================
+ Hits       181860   181920   +60     
+ Misses      40402    40337   -65     

[steviez]

Looks good to me. Can you confirm this still works as intended? (I wasn't familiar with the lines() stuff, which is why I didn't do this one myself heh.)

Can confirm - lines() returns an iterator that yields Result<String, Error>. Calling .flatten() on that yields the Ok(String)s and skips the Err(...)s.

On the other hand, calling map_while() directly yields us all Ok(String)s until we hit an Err(...). So, technically a slight change in behavior in that the old method would continue past an error (potentially infinitely per the lint) while the new approach will halt at first error. An error would be something like the read bytes not being valid UTF-8 or some low level error with the file; I think bailing on either of these events is just fine.