feat(gnovm/tests/stdlibs): add fmt

[thehowl]

This PR removes fmt from being implemented using NativeValue / NativeType, and implements a mostly pure-Gno implementation which uses an initial, rudimentary implementation of Gno reflection for fmt.

This PR is ready for review, but some of its related work has been broken out in separate PR to aid reviewing and create atomic PRs.

• Blocks chore: remove All nativeType and nativeValues #3677
• Relates to [chore] Remove NativeValue and NativeType from the VM entirely #1361
• Depends on fix(gnovm): handle calling method with value receiver on nil #3861
• Depends on feat(gnovm): add any type #3862
• Depends on feat(gnovm): improve interface/func/struct type String methods #3875

Summary of changes

addition of gnovm/tests/stdlibs/fmt

The main addition is of this set of files, which comprises the bulk of the added lines of this PR. Most of this is a copy of Go's fmt. Changes are mostly in errors.gno and format.gno - the other files are left mostly intact.

At the end of print.gno, there is an added section containing a set of native functions which form the "reflection" needed to implement the fmt package in a manner that is similar to Go's. The implementation is not meant to be a public API and is meant to serve initially only for usage by fmt; we can use this as sketch to then implement a proper reflect package.

Attention in reviewing should mostly go to this print.gno and its print.go counterpart, especially for any missed cases or potential bugs.

addition of gnovm/tests/stdlibs/os

Complementary to the above, to avoid some problems that were arising due to the handling of os.Stdin, Stdout and Stderr, I also removed the NativeValue / NativeType in os and replaced them with a native binding alternative.

To avoid having both an Output and ErrorOutput on the machine, this package supports an additional method on the Machine.Output, StderrWrite, which is implemented by writers who wish to differentiate between the two.

other

• gnovm/pkg/test
  • added support for StderrWrite in its writers
  • removed native values for os and fmt
  • combine stdin, stdout, stderr into a single output parameter in the related functions.
• gnovm/pkg/gnolang
  • support testing gnovm/tests/stdlibs, by only testing stdlibs that exist there and not in the official stdlibs.
• gnovm/cmd/gno
  • fix tests which needed the fmt package.
• gnovm/tests/files
  • most changed tests are result of the improved functionality of the fmt package, allowing for instance to show declared types correctly.
• gnovm/stdlibs/bufio
  • due to the removal of os.Stdin, this example had to be changed.
• misc/genstd
  • added a flag -skip-init-order when creating it could cause problems, like the testing stdlibs; fixed a bug when using TypedValue.

[Gno2D2]

🛠 PR Checks Summary

All Automated Checks passed. ✅

Manual Checks (for Reviewers):

• IGNORE the bot requirements for this PR (force green CI check)

Read More

🤖 This bot helps streamline PR reviews by verifying automated checks and providing guidance for contributors and reviewers.

✅ Automated Checks (for Contributors):

🟢 Maintainers must be able to edit this pull request (more info)

☑️ Contributor Actions:

1. Fix any issues flagged by automated checks.
2. Follow the Contributor Checklist to ensure your PR is ready for review.
   • Add new tests, or document why they are unnecessary.
   • Provide clear examples/screenshots, if necessary.
   • Update documentation, if required.
   • Ensure no breaking changes, or include BREAKING CHANGE notes.
   • Link related issues/PRs, where applicable.

☑️ Reviewer Actions:

1. Complete manual checks for the PR, including the guidelines and additional checks if applicable.

📚 Resources:

• Report a bug with the bot.
• View the bot’s configuration file.

Debug

Automated Checks

Maintainers must be able to edit this pull request (more info)

If

🟢 Condition met
└── 🟢 And
    ├── 🟢 The base branch matches this pattern: ^master$
    └── 🟢 The pull request was created from a fork (head branch repo: thehowl/gno)

Then

🟢 Requirement satisfied
└── 🟢 Maintainer can modify this pull request

Manual Checks

**IGNORE** the bot requirements for this PR (force green CI check)

If

🟢 Condition met
└── 🟢 On every pull request

Can be checked by

• Any user with comment edit permission

[codecov]

Codecov Report

Attention: Patch coverage is 84.08163% with 39 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
gnovm/tests/stdlibs/fmt/print.go	82.14%	30 Missing and 5 partials ⚠️
misc/genstd/genstd.go	57.14%	3 Missing ⚠️
gnovm/pkg/test/test.go	95.23%	1 Missing ⚠️

📢 Thoughts on this report? Let us know!

[ltzmaxwell]

After comparing with the native Go fmt, it follows the original design, and the mini reflection implemented through nativebinding is cleverly designed. LGTM.

[mvertes]

Incidentally, I think that this PR may also solve #3687, through implementation of X_getAddr() in gnovm/tests/sdtlibs/fmt/print.go although I haven't yet verified it.

[mvertes]

LGTM

[thehowl]

Incidentally, I think that this PR may also solve #3687, through implementation of X_getAddr() in gnovm/tests/sdtlibs/fmt/print.go although I haven't yet verified it.

That issue is still valid for println(), and the implementation of getAddr is actually non-deterministic; but it's fine because fmt can only be used off-chain.

When we move fmt on-chain (or better, when we make a proper reflect implementation), I'd like to figure out a way to make a proper deterministic getAddr implementation.