cmd/go: make module suggestion more friendly

We are trying to avoid by not automatically updating go.mod. The
suggestion should be that users actually add the dependencies they
need, and the command in an easily copy-pastable form now.

Fixes: #43430

Change-Id: I2227dab498fcd8d66184c94ebe9e776629ccadfd
Reviewed-on: https://go-review.googlesource.com/c/go/+/280713
Run-TryBot: Baokun Lee <bk@golangcn.org>
Run-TryBot: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Jay Conrod <jayconrod@google.com>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
Trust: Jay Conrod <jayconrod@google.com>
Trust: Bryan C. Mills <bcmills@google.com>

src/cmd/go/internal/modload/import.go

@@ -31,10 +31,6 @@ type ImportMissingError struct {
 	Module   module.Version
 	QueryErr error
 
-	// inAll indicates whether Path is in the "all" package pattern,
-	// and thus would be added by 'go mod tidy'.
-	inAll bool
-
 	// isStd indicates whether we would expect to find the package in the standard
 	// library. This is normally true for all dotless import paths, but replace
 	// directives can cause us to treat the replaced paths as also being in
@@ -67,16 +63,14 @@ func (e *ImportMissingError) Error() string {
 			if !modfetch.IsZeroPseudoVersion(e.replaced.Version) {
 				suggestArg = e.replaced.String()
 			}
-			return fmt.Sprintf("module %s provides package %s and is replaced but not required; try 'go get -d %s' to add it", e.replaced.Path, e.Path, suggestArg)
+			return fmt.Sprintf("module %s provides package %s and is replaced but not required; to add it:\n\tgo get %s", e.replaced.Path, e.Path, suggestArg)
 		}
 
 		suggestion := ""
 		if !HasModRoot() {
 			suggestion = ": working directory is not part of a module"
-		} else if e.inAll {
-			suggestion = "; try 'go mod tidy' to add it"
 		} else {
-			suggestion = fmt.Sprintf("; try 'go get -d %s' to add it", e.Path)
+			suggestion = fmt.Sprintf("; to add it:\n\tgo get %s", e.Path)
 		}
 		return fmt.Sprintf("no required module provides package %s%s", e.Path, suggestion)
 	}
@@ -151,7 +145,7 @@ func (e *ImportMissingSumError) Error() string {
 		message = fmt.Sprintf("missing go.sum entry for module providing package %s", e.importPath)
 	}
 	if e.inAll {
-		return message + "; try 'go mod tidy' to add it"
+		return message + "; to add it:\n\tgo mod tidy"
 	}
 	return message
 }

src/cmd/go/internal/modload/init.go

@@ -458,7 +458,7 @@ func CreateModFile(ctx context.Context, modPath string) {
 		}
 	}
 	if !empty {
-		fmt.Fprintf(os.Stderr, "go: run 'go mod tidy' to add module requirements and sums\n")
+		fmt.Fprintf(os.Stderr, "go: to add module requirements and sums:\n\tgo mod tidy\n")
 	}
 }
 
@@ -907,7 +907,7 @@ func WriteGoMod() {
 		} else if cfg.BuildModReason != "" {
 			base.Fatalf("go: updates to go.mod needed, disabled by -mod=readonly\n\t(%s)", cfg.BuildModReason)
 		} else {
-			base.Fatalf("go: updates to go.mod needed; try 'go mod tidy' first")
+			base.Fatalf("go: updates to go.mod needed; to update it:\n\tgo mod tidy")
 		}
 	}
 

src/cmd/go/internal/modload/load.go

@@ -281,9 +281,7 @@ func LoadPackages(ctx context.Context, opts PackageOpts, patterns ...string) (ma
 	for _, pkg := range loaded.pkgs {
 		if pkg.err != nil {
 			if pkg.flags.has(pkgInAll) {
-				if imErr := (*ImportMissingError)(nil); errors.As(pkg.err, &imErr) {
+				if sumErr := (*ImportMissingSumError)(nil); errors.As(pkg.err, &sumErr) {
-					imErr.inAll = true
-				} else if sumErr := (*ImportMissingSumError)(nil); errors.As(pkg.err, &sumErr) {
 					sumErr.inAll = true
 				}
 			}

src/cmd/go/internal/modload/modfile.go

@@ -449,7 +449,7 @@ func goModSummary(m module.Version) (*modFileSummary, error) {
 	if HasModRoot() && cfg.BuildMod == "readonly" && actual.Version != "" {
 		key := module.Version{Path: actual.Path, Version: actual.Version + "/go.mod"}
 		if !modfetch.HaveSum(key) {
-			suggestion := fmt.Sprintf("; try 'go mod download %s' to add it", m.Path)
+			suggestion := fmt.Sprintf("; to add it:\n\tgo mod download %s", m.Path)
 			return nil, module.VersionError(actual, &sumMissingError{suggestion: suggestion})
 		}
 	}

src/cmd/go/testdata/script/mod_bad_domain.txt

@@ -19,7 +19,7 @@ stderr 'malformed module path "x/y.z": missing dot in first path element'
 ! go build ./useappengine
 stderr '^useappengine[/\\]x.go:2:8: cannot find package$'
 ! go build ./usenonexistent
-stderr '^usenonexistent[/\\]x.go:2:8: no required module provides package nonexistent.rsc.io; try ''go mod tidy'' to add it$'
+stderr '^usenonexistent[/\\]x.go:2:8: no required module provides package nonexistent.rsc.io; to add it:\n\tgo get nonexistent.rsc.io$'
 
 
 # 'get -d' should be similarly definitive

src/cmd/go/testdata/script/mod_get_replaced.txt

@@ -87,7 +87,7 @@ stderr '^go get: malformed module path "example": missing dot in first path elem
 go mod edit -replace example@v0.1.0=./example
 
 ! go list example
-stderr '^module example provides package example and is replaced but not required; try ''go get -d example@v0.1.0'' to add it$'
+stderr '^module example provides package example and is replaced but not required; to add it:\n\tgo get example@v0.1.0$'
 
 go get -d example
 go list -m example

src/cmd/go/testdata/script/mod_gobuild_import.txt

@@ -19,7 +19,7 @@ exec $WORK/testimport$GOEXE other/x/y/z/w .
 stdout w2.go
 
 ! exec $WORK/testimport$GOEXE gobuild.example.com/x/y/z/w .
-stderr 'no required module provides package gobuild.example.com/x/y/z/w; try ''go get -d gobuild.example.com/x/y/z/w'' to add it'
+stderr 'no required module provides package gobuild.example.com/x/y/z/w; to add it:\n\tgo get gobuild.example.com/x/y/z/w'
 
 cd z
 exec $WORK/testimport$GOEXE other/x/y/z/w .

src/cmd/go/testdata/script/mod_init_tidy.txt

@@ -8,14 +8,14 @@ cd ..
 # 'go mod init' should recommend 'go mod tidy' if the directory has a .go file.
 cd pkginroot
 go mod init m
-stderr '^go: run ''go mod tidy'' to add module requirements and sums$'
+stderr '^go: to add module requirements and sums:\n\tgo mod tidy$'
 cd ..
 
 # 'go mod init' should recommend 'go mod tidy' if the directory has a
 # subdirectory. We don't walk the tree to see if it has .go files.
 cd subdir
 go mod init m
-stderr '^go: run ''go mod tidy'' to add module requirements and sums$'
+stderr '^go: to add module requirements and sums:\n\tgo mod tidy$'
 cd ..
 
 -- empty/empty.txt --

src/cmd/go/testdata/script/mod_install_pkg_version.txt

@@ -16,7 +16,7 @@ env GO111MODULE=auto
 cd m
 cp go.mod go.mod.orig
 ! go list -m all
-stderr '^go: example.com/cmd@v1.1.0-doesnotexist: missing go.sum entry; try ''go mod download example.com/cmd'' to add it$'
+stderr '^go: example.com/cmd@v1.1.0-doesnotexist: missing go.sum entry; to add it:\n\tgo mod download example.com/cmd$'
 go install example.com/cmd/a@latest
 cmp go.mod go.mod.orig
 exists $GOPATH/bin/a$GOEXE
@@ -67,9 +67,9 @@ cd tmp
 go mod init tmp
 go mod edit -require=rsc.io/fortune@v1.0.0
 ! go install -mod=readonly $GOPATH/pkg/mod/rsc.io/fortune@v1.0.0
-stderr '^go: rsc.io/fortune@v1.0.0: missing go.sum entry; try ''go mod download rsc.io/fortune'' to add it$'
+stderr '^go: rsc.io/fortune@v1.0.0: missing go.sum entry; to add it:\n\tgo mod download rsc.io/fortune$'
 ! go install -mod=readonly ../../pkg/mod/rsc.io/fortune@v1.0.0
-stderr '^go: rsc.io/fortune@v1.0.0: missing go.sum entry; try ''go mod download rsc.io/fortune'' to add it$'
+stderr '^go: rsc.io/fortune@v1.0.0: missing go.sum entry; to add it:\n\tgo mod download rsc.io/fortune$'
 go get -d rsc.io/fortune@v1.0.0
 go install -mod=readonly $GOPATH/pkg/mod/rsc.io/fortune@v1.0.0
 exists $GOPATH/bin/fortune$GOEXE

src/cmd/go/testdata/script/mod_list_bad_import.txt

@@ -39,7 +39,7 @@ stdout example.com/notfound
 
 # Listing the missing dependency directly should fail outright...
 ! go list -f '{{if .Error}}error{{end}} {{if .Incomplete}}incomplete{{end}}' example.com/notfound
-stderr 'no required module provides package example.com/notfound; try ''go get -d example.com/notfound'' to add it'
+stderr 'no required module provides package example.com/notfound; to add it:\n\tgo get example.com/notfound'
 ! stdout error
 ! stdout incomplete
 

src/cmd/go/testdata/script/mod_readonly.txt

@@ -13,7 +13,7 @@ cmp go.mod go.mod.empty
 # -mod=readonly should be set by default.
 env GOFLAGS=
 ! go list all
-stderr '^x.go:2:8: no required module provides package rsc\.io/quote; try ''go mod tidy'' to add it$'
+stderr '^x.go:2:8: no required module provides package rsc\.io/quote; to add it:\n\tgo get rsc\.io/quote$'
 cmp go.mod go.mod.empty
 
 env GOFLAGS=-mod=readonly
@@ -51,7 +51,7 @@ cmp go.mod go.mod.inconsistent
 # We get a different message when -mod=readonly is used by default.
 env GOFLAGS=
 ! go list
-stderr '^go: updates to go.mod needed; try ''go mod tidy'' first$'
+stderr '^go: updates to go.mod needed; to update it:\n\tgo mod tidy'
 
 # However, it should not reject files missing a 'go' directive,
 # since that was not always required.
@@ -75,15 +75,15 @@ cmp go.mod go.mod.indirect
 
 cp go.mod.untidy go.mod
 ! go list all
-stderr '^x.go:2:8: no required module provides package rsc.io/quote; try ''go mod tidy'' to add it$'
+stderr '^x.go:2:8: no required module provides package rsc.io/quote; to add it:\n\tgo get rsc.io/quote$'
 
 ! go list -deps .
-stderr '^x.go:2:8: no required module provides package rsc.io/quote; try ''go mod tidy'' to add it$'
+stderr '^x.go:2:8: no required module provides package rsc.io/quote; to add it:\n\tgo get rsc.io/quote$'
 
 # However, if we didn't see an import from the main module, we should suggest
 # 'go get -d' instead, because we don't know whether 'go mod tidy' would add it.
 ! go list rsc.io/quote
-stderr '^no required module provides package rsc.io/quote; try ''go get -d rsc.io/quote'' to add it$'
+stderr '^no required module provides package rsc.io/quote; to add it:\n\tgo get rsc.io/quote$'
 
 
 -- go.mod --

src/cmd/go/testdata/script/mod_replace_readonly.txt

@@ -9,7 +9,7 @@ cp go.mod go.mod.orig
 # can't in readonly mode, since its go.mod may alter the build list.
 go mod edit -replace rsc.io/quote=./quote
 ! go list rsc.io/quote
-stderr '^module rsc.io/quote provides package rsc.io/quote and is replaced but not required; try ''go get -d rsc.io/quote'' to add it$'
+stderr '^module rsc.io/quote provides package rsc.io/quote and is replaced but not required; to add it:\n\tgo get rsc.io/quote$'
 go get -d rsc.io/quote
 cmp go.mod go.mod.latest
 go list rsc.io/quote
@@ -18,7 +18,7 @@ cp go.mod.orig go.mod
 # Same test with a specific version.
 go mod edit -replace rsc.io/quote@v1.0.0-doesnotexist=./quote
 ! go list rsc.io/quote
-stderr '^module rsc.io/quote provides package rsc.io/quote and is replaced but not required; try ''go get -d rsc.io/quote@v1.0.0-doesnotexist'' to add it$'
+stderr '^module rsc.io/quote provides package rsc.io/quote and is replaced but not required; to add it:\n\tgo get rsc.io/quote@v1.0.0-doesnotexist$'
 go get -d rsc.io/quote@v1.0.0-doesnotexist
 cmp go.mod go.mod.specific
 go list rsc.io/quote
@@ -28,7 +28,7 @@ cp go.mod.orig go.mod
 go mod edit -replace rsc.io/quote@v1.0.0-doesnotexist=./quote
 go mod edit -replace rsc.io/quote@v1.1.0-doesnotexist=./quote
 ! go list rsc.io/quote
-stderr '^module rsc.io/quote provides package rsc.io/quote and is replaced but not required; try ''go get -d rsc.io/quote@v1.1.0-doesnotexist'' to add it$'
+stderr '^module rsc.io/quote provides package rsc.io/quote and is replaced but not required; to add it:\n\tgo get rsc.io/quote@v1.1.0-doesnotexist$'
 
 -- go.mod --
 module m

src/cmd/go/testdata/script/mod_sum_ambiguous.txt

@@ -17,13 +17,13 @@ cp go.sum.a-only go.sum
 ! go list example.com/ambiguous/a/b
 stderr '^missing go.sum entry needed to verify package example.com/ambiguous/a/b is provided by exactly one module$'
 ! go list -deps .
-stderr '^use.go:3:8: missing go.sum entry needed to verify package example.com/ambiguous/a/b is provided by exactly one module; try ''go mod tidy'' to add it$'
+stderr '^use.go:3:8: missing go.sum entry needed to verify package example.com/ambiguous/a/b is provided by exactly one module; to add it:\n\tgo mod tidy$'
 
 cp go.sum.b-only go.sum
 ! go list example.com/ambiguous/a/b
 stderr '^missing go.sum entry for module providing package example.com/ambiguous/a/b$'
 ! go list -deps .
-stderr '^use.go:3:8: missing go.sum entry for module providing package example.com/ambiguous/a/b; try ''go mod tidy'' to add it$'
+stderr '^use.go:3:8: missing go.sum entry for module providing package example.com/ambiguous/a/b; to add it:\n\tgo mod tidy$'
 
 -- go.mod --
 module m

src/cmd/go/testdata/script/mod_sum_readonly.txt

@@ -4,7 +4,7 @@ env GO111MODULE=on
 # When a sum is needed to load the build list, we get an error for the
 # specific module. The .mod file is not downloaded, and go.sum is not written.
 ! go list -m all
-stderr '^go: rsc.io/quote@v1.5.2: missing go.sum entry; try ''go mod download rsc.io/quote'' to add it$'
+stderr '^go: rsc.io/quote@v1.5.2: missing go.sum entry; to add it:\n\tgo mod download rsc.io/quote$'
 ! exists $GOPATH/pkg/mod/cache/download/rsc.io/quote/@v/v1.5.2.mod
 ! exists go.sum
 
@@ -12,7 +12,7 @@ stderr '^go: rsc.io/quote@v1.5.2: missing go.sum entry; try ''go mod download rs
 # we should see the same error.
 cp go.sum.h2only go.sum
 ! go list -m all
-stderr '^go: rsc.io/quote@v1.5.2: missing go.sum entry; try ''go mod download rsc.io/quote'' to add it$'
+stderr '^go: rsc.io/quote@v1.5.2: missing go.sum entry; to add it:\n\tgo mod download rsc.io/quote$'
 ! exists $GOPATH/pkg/mod/cache/download/rsc.io/quote/@v/v1.5.2.mod
 cmp go.sum go.sum.h2only
 rm go.sum
@@ -21,7 +21,7 @@ rm go.sum
 cp go.mod go.mod.orig
 go mod edit -replace rsc.io/quote@v1.5.2=rsc.io/quote@v1.5.1
 ! go list -m all
-stderr '^go: rsc.io/quote@v1.5.2 \(replaced by rsc.io/quote@v1.5.1\): missing go.sum entry; try ''go mod download rsc.io/quote'' to add it$'
+stderr '^go: rsc.io/quote@v1.5.2 \(replaced by rsc.io/quote@v1.5.1\): missing go.sum entry; to add it:\n\tgo mod download rsc.io/quote$'
 ! exists $GOPATH/pkg/mod/cache/download/rsc.io/quote/@v/v1.5.1.mod
 ! exists go.sum
 cp go.mod.orig go.mod
@@ -35,7 +35,7 @@ exists $GOPATH/pkg/mod/cache/download/rsc.io/quote/@v/v1.5.2.mod
 # When a sum is needed to load a .mod file for a package outside the build list,
 # we get a generic missing import error.
 ! go list example.com/doesnotexist
-stderr '^no required module provides package example.com/doesnotexist; try ''go get -d example.com/doesnotexist'' to add it$'
+stderr '^no required module provides package example.com/doesnotexist; to add it:\n\tgo get example.com/doesnotexist$'
 
 # When a sum is needed to load a .zip file, we get a more specific error.
 # The .zip file is not downloaded.
@@ -47,7 +47,7 @@ stderr '^missing go.sum entry for module providing package rsc.io/quote$'
 # a package that imports it without that error.
 go list -e -deps -f '{{.ImportPath}}{{with .Error}} {{.Err}}{{end}}' .
 stdout '^m$'
-stdout '^rsc.io/quote missing go.sum entry for module providing package rsc.io/quote; try ''go mod tidy'' to add it$'
+stdout '^rsc.io/quote missing go.sum entry for module providing package rsc.io/quote; to add it:\n\tgo mod tidy$'
 ! exists $GOPATH/pkg/mod/cache/download/rsc.io/quote/@v/v1.5.2.zip
 
 # go.sum should not have been written.