x/exp/cmd/gorelease: avoid using -mod=mod and support lazy module loading

Details:

- Replaces `go list -mod=mod` with `go list -mod=readonly`.
- Switches to `go get -d` to download dependencies rather than relying on `go
  list` doing so.
- Missing go.sum/go.mod data is now an error.

This CL will be followed by a CL that ensures the filepath.Walk stops at
submodules, and a test asserting that. I figured it'd be good to do separately
since this CL is getting to be hefty. Give a shout if you prefer otherwise!

Updates golang/go#41456

Change-Id: I66f12fe0325e4fed432d8b10c1fe977068e4a030
Reviewed-on: https://go-review.googlesource.com/c/exp/+/263178
Run-TryBot: Jean de Klerk <[email protected]>
TryBot-Result: Go Bot <[email protected]>
Reviewed-by: Jay Conrod <[email protected]>
Trust: Jean de Klerk <[email protected]>

Author: jeanbza

cmd/gorelease/gorelease.go

@@ -52,10 +52,30 @@ func hasFilePathPrefix(s, prefix string) bool {
 	}
 }
 
+// trimFilePathPrefix returns the given filesystem path s without the leading
+// prefix.
+func trimFilePathPrefix(s, prefix string) string {
+	sv := strings.ToUpper(filepath.VolumeName(s))
+	pv := strings.ToUpper(filepath.VolumeName(prefix))
+	s = s[len(sv):]
+	prefix = prefix[len(pv):]
+
+	if !hasFilePathPrefix(s, prefix) || len(prefix) == 0 {
+		return s
+	}
+	if len(s) == len(prefix) {
+		return ""
+	}
+	if prefix[len(prefix)-1] == filepath.Separator {
+		return strings.TrimPrefix(s, prefix)
+	}
+	return s[len(prefix)+1:]
+}
+
 // trimPathPrefix returns p without the leading prefix. Unlike
-// strings.TrimPrefix, the prefix will only match on slash-separted comopnent
+// strings.TrimPrefix, the prefix will only match on slash-separted component
 // boundaries, so trimPathPrefix("aa/b", "aa") returns "b", but
-// trimPathPrefix("aa/b", "a") retunrs "aa/b".
+// trimPathPrefix("aa/b", "a") returns "aa/b".
 func trimPathPrefix(p, prefix string) string {
 	if prefix == "" {
 		return p

cmd/gorelease/path.go

@@ -113,6 +113,80 @@ func TestHasFilePathPrefix(t *testing.T) {
 	}
 }
 
+func TestTrimFilePathPrefix(t *testing.T) {
+	type test struct {
+		desc, path, prefix, want string
+	}
+	var tests []test
+	if runtime.GOOS == "windows" {
+		tests = []test{
+			// Note: these two cases in which the result preserves the leading \
+			// don't come up in reality in gorelease. That's because prefix is
+			// always far to the right of the path parts (ex github.com/foo/bar
+			// in C:\Users\foo\AppData\Local\Temp\...\github.com\foo\bar).
+			{
+				desc:   "empty_prefix",
+				path:   `c:\a\b`,
+				prefix: "",
+				want:   `\a\b`,
+			}, {
+				desc:   "partial_component",
+				path:   `c:\aa\b`,
+				prefix: `c:\a`,
+				want:   `\aa\b`,
+			},
+
+			{
+				desc:   "drive_prefix",
+				path:   `c:\a\b`,
+				prefix: `c:\`,
+				want:   `a\b`,
+			}, {
+				desc:   "partial_prefix",
+				path:   `c:\a\b`,
+				prefix: `c:\a`,
+				want:   `b`,
+			}, {
+				desc:   "full_prefix",
+				path:   `c:\a\b`,
+				prefix: `c:\a\b`,
+				want:   "",
+			},
+		}
+	} else {
+		tests = []test{
+			{
+				desc:   "empty_prefix",
+				path:   "/a/b",
+				prefix: "",
+				want:   "/a/b",
+			}, {
+				desc:   "partial_prefix",
+				path:   "/a/b",
+				prefix: "/a",
+				want:   "b",
+			}, {
+				desc:   "full_prefix",
+				path:   "/a/b",
+				prefix: "/a/b",
+				want:   "",
+			}, {
+				desc:   "partial_component",
+				path:   "/aa/b",
+				prefix: "/a",
+				want:   "/aa/b",
+			},
+		}
+	}
+	for _, test := range tests {
+		t.Run(test.desc, func(t *testing.T) {
+			if got := trimFilePathPrefix(test.path, test.prefix); got != test.want {
+				t.Errorf("hasFilePathPrefix(%q, %q): got %v, want %v", test.path, test.prefix, got, test.want)
+			}
+		})
+	}
+}
+
 func TestTrimPathPrefix(t *testing.T) {
 	for _, test := range []struct {
 		desc, path, prefix, want string

cmd/gorelease/path_test.go

@@ -1,9 +1,8 @@
 mod=example.com/tidy
 base=v0.0.1
-success=0
+success=false
 -- want --
-go.sum: one or more sums are missing.
-Run 'go mod tidy' to add missing sums.
+go.sum: one or more sums are missing. Run 'go mod tidy' to add missing sums.
 -- go.mod --
 module example.com/tidy
 

cmd/gorelease/testdata/tidy/empty_sum.test

@@ -0,0 +1,26 @@
+mod=example.com/tidy
+base=v0.0.1
+success=false
+-- want --
+example.com/tidy/subdir
+-----------------------
+Compatible changes:
+- package added
+
+go.mod: the following requirements are needed
+	example.com/[email protected]
+Run 'go mod tidy' to add missing requirements.
+-- go.mod --
+module example.com/tidy
+
+go 1.12
+-- go.mod --
+module example.com/tidy
+
+go 1.12
+-- tidy.go --
+package tidy
+-- subdir/tidy.go --
+package subpkg
+
+import _ "example.com/basic/a"

cmd/gorelease/testdata/tidy/missing_req.test renamed to cmd/gorelease/testdata/tidy/missing_req_basic.test

@@ -0,0 +1,26 @@
+mod=example.com/tidy
+base=v0.0.1
+success=false
+-- want --
+example.com/tidy/subdir/subsubdir
+---------------------------------
+Compatible changes:
+- package added
+
+go.mod: the following requirements are needed
+	example.com/[email protected]
+Run 'go mod tidy' to add missing requirements.
+-- go.mod --
+module example.com/tidy
+
+go 1.12
+-- go.mod --
+module example.com/tidy
+
+go 1.12
+-- tidy.go --
+package tidy
+-- subdir/subsubdir/tidy.go --
+package subpkg
+
+import _ "example.com/basic/a"

cmd/gorelease/testdata/tidy/missing_req_nested.test

@@ -1,9 +1,8 @@
 mod=example.com/tidy
 base=v0.0.1
-success=0
+success=false
 -- want --
-go.sum: one or more sums are missing.
-Run 'go mod tidy' to add missing sums.
+go.sum: one or more sums are missing. Run 'go mod tidy' to add missing sums.
 -- go.mod --
 module example.com/tidy