#moondiff

Difftool that aware MoonBit language syntax.

Inspired by difftastic

Try it in playground: https://moonbit-community.github.io/moondiff/

#CLI

moondiff [--ignore-comments] [--ignore-tests] old-file new-file

--ignore-tests is off by default. If either path ends in _test.mbt or _wbtest.mbt (case-sensitive), the entire comparison is ignored before parsing, including helper functions, imports, and invalid syntax. This also covers additions, deletions (/dev/null), and renames to or from ordinary files. File headers remain visible with an ignored-file notice; identical content still reports no changes.

For other pairs where both paths end in .mbt, after both inputs parse successfully, top-level test and async test blocks are removed from lexical and AST comparison, together with their leading documentation comments, ///|UUID(...) markers, and ///| separators. Test-only changes report no changes; when production code also changes, only that production change is highlighted. Imports such as import { ... } for "test" remain ordinary source and are still compared.

--ignore-comments independently excludes comments and blank-line-only changes. The flags can be combined. If either MoonBit input fails to parse, the CLI retains its existing whole-file lexical fallback unless a test-file path matched; test-block filtering is not guaranteed in that fallback. Other pairs, including ordinary .mbt/text comparisons and ordinary .mbt additions or deletions, go directly to the plain line diff without MoonBit parsing and are unaffected by either MoonBit filter.

The library's mbtdiff.diff uses old_name and new_name for both path filtering and parser diagnostics. With DiffOptions(ignore_tests=true), a matching path returns IgnoredOnly, an empty Whole document, and no fallbacks when content differs; Identical retains priority. Omitting names keeps the defaults "old" and "new" and only applies test-block filtering. DiffResult.ignore_reason() returns Some(TestFile) for a whole-file exclusion and Some(FilteredContent) when content filters exclude all changes. Other statuses return None. The CLI uses the shared internal test-file path rule to decide whether MoonBit calculation is needed; displayed statuses and ignore notices still come from the core result.

For reliably aligned MoonBit declarations, each CLI section title ends with the trimmed source line containing that declaration's keyword, and every visible @@ ... @@ hunk heading repeats the same context. Matching old/new lines are shown once; changed declaration lines are rendered as old: … → new: …. Leading documentation, UUID markers, separators, and standalone attribute lines are not used as the context. Whole-file results, including parse-failure fallbacks, and ordinary text diffs do not attach a top-level declaration context.

#install (unfinish)

#Use Moondiff in Git Repository (unfinish)

configure git to use the installed wasm as an optional diff tool within that repository:

git config diff.tool moondiff
git config difftool.moondiff.cmd 'bash "$HOME/.local/share/moondiff/moondiff_git_wrapper.sh" "$LOCAL" "$REMOTE" "$MERGED"'
git config difftool.prompt false

usage:

git difftool <commit>^ <commit> # view diff for a specific commit
git difftool <edited file>

Source Files

main.mbt

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