Documentation
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Overview ¶
Package modernize providers the modernizer analyzer.
Analyzer modernize ¶
modernize: simplify code by using modern constructs
This analyzer reports opportunities for simplifying and clarifying existing code by using more modern features of Go and its standard library.
Each diagnostic provides a fix. Our intent is that these fixes may be safely applied en masse without changing the behavior of your program. In some cases the suggested fixes are imperfect and may lead to (for example) unused imports or unused local variables, causing build breakage. However, these problems are generally trivial to fix. We regard any modernizer whose fix changes program behavior to have a serious bug and will endeavor to fix it.
To apply all modernization fixes en masse, you can use the following command:
$ go run golang.org/x/tools/gopls/internal/analysis/modernize/cmd/modernize@latest -fix -test ./...
(Do not use "go get -tool" to add gopls as a dependency of your module; gopls commands must be built from their release branch.)
If the tool warns of conflicting fixes, you may need to run it more than once until it has applied all fixes cleanly. This command is not an officially supported interface and may change in the future.
Changes produced by this tool should be reviewed as usual before being merged. In some cases, a loop may be replaced by a simple function call, causing comments within the loop to be discarded. Human judgment may be required to avoid losing comments of value.
Each diagnostic reported by modernize has a specific category. (The categories are listed below.) Diagnostics in some categories, such as "efaceany" (which replaces "interface{}" with "any" where it is safe to do so) are particularly numerous. It may ease the burden of code review to apply fixes in two passes, the first change consisting only of fixes of category "efaceany", the second consisting of all others. This can be achieved using the -category flag:
$ modernize -category=efaceany -fix -test ./... $ modernize -category=-efaceany -fix -test ./...
Categories of modernize diagnostic:
forvar: remove x := x variable declarations made unnecessary by the new semantics of loops in go1.22.
slicescontains: replace 'for i, elem := range s { if elem == needle { ...; break }' by a call to slices.Contains, added in go1.21.
minmax: replace an if/else conditional assignment by a call to the built-in min or max functions added in go1.21.
sortslice: replace sort.Slice(x, func(i, j int) bool) { return s[i] < s[j] } by a call to slices.Sort(s), added in go1.21.
efaceany: replace interface{} by the 'any' type added in go1.18.
mapsloop: replace a loop around an m[k]=v map update by a call to one of the Collect, Copy, Clone, or Insert functions from the maps package, added in go1.21.
fmtappendf: replace []byte(fmt.Sprintf...) by fmt.Appendf(nil, ...), added in go1.19.
testingcontext: replace uses of context.WithCancel in tests with t.Context, added in go1.24.
omitzero: replace omitempty by omitzero on structs, added in go1.24.
bloop: replace "for i := range b.N" or "for range b.N" in a benchmark with "for b.Loop()", and remove any preceding calls to b.StopTimer, b.StartTimer, and b.ResetTimer.
B.Loop intentionally defeats compiler optimizations such as inlining so that the benchmark is not entirely optimized away. Currently, however, it may cause benchmarks to become slower in some cases due to increased allocation; see https://go.dev/issue/73137.
rangeint: replace a 3-clause "for i := 0; i < n; i++" loop by "for i := range n", added in go1.22.
stringsseq: replace Split in "for range strings.Split(...)" by go1.24's more efficient SplitSeq, or Fields with FieldSeq.
stringscutprefix: replace some uses of HasPrefix followed by TrimPrefix with CutPrefix, added to the strings package in go1.20.
waitgroup: replace old complex usages of sync.WaitGroup by less complex WaitGroup.Go method in go1.25.
Index ¶
Constants ¶
This section is empty.
Variables ¶
var Analyzer = &analysis.Analyzer{ Name: "modernize", Doc: analysisinternal.MustExtractDoc(doc, "modernize"), Requires: []*analysis.Analyzer{inspect.Analyzer, typeindexanalyzer.Analyzer}, Run: run, URL: "https://pkg.go.dev/golang.org/x/tools/gopls/internal/analysis/modernize", }
var EnableAppendClipped = false
append(clipped, ...) cannot be replaced by slices.Concat (etc) without more attention to preservation of nilness; see #73557. Until we either fix it or revise our safety goals, we disable this analyzer for now.
Its former documentation in doc.go was:
- appendclipped: replace append([]T(nil), s...) by slices.Clone(s) or slices.Concat(s), added in go1.21.
var EnableSlicesDelete = false
slices.Delete is not equivalent to append(s[:i], [j:]...): it clears the vacated array slots; see #73686. Until we either fix it or revise our safety goals, we disable this analyzer for now.
Its former documentation in doc.go was:
- slicesdelete: replace append(s[:i], s[i+1]...) by slices.Delete(s, i, i+1), added in go1.21.
Functions ¶
This section is empty.
Types ¶
This section is empty.
Source Files
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