cmd/cue: check the structure of CUE_CACHE_DIR after downloading modules

This acts as a nice regression test and visualization, and we will see
the impact of future changes like https://cuelang.org/issue/3139.

Note that ./mod/modcache already covers the presence of specific cache
files via its Go unit tests, but this added testscript check is a nice
complement which covers all files and shows the entire structure.

For #3139.

Signed-off-by: Daniel Martí <[email protected]>
Change-Id: I2ffa32f7ccb44b52c0bfad1bfe56f93a450d5a70
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1195517
Unity-Result: CUE porcuepine <[email protected]>
Reviewed-by: Paul Jolly <[email protected]>
TryBot-Result: CUEcueckoo <[email protected]>

cmd/cue/cmd/script_test.go

@@ -204,7 +204,7 @@ func TestScript(t *testing.T) {
 			//   responds with [tokenErrorCodePending] once, and then succeeds
 			// * immediate-success: polling for a token with device_code succeeds right away
 			"oauthregistry": func(ts *testscript.TestScript, neg bool, args []string) {
-				if len(args) != 1 {
+				if neg || len(args) != 1 {
 					ts.Fatalf("usage: oauthregistry <mode>")
 				}
 				ts.Setenv("CUE_EXPERIMENT", "modules")
@@ -213,6 +213,30 @@ func TestScript(t *testing.T) {
 				ts.Setenv("CUE_REGISTRY", u.Host+"+insecure")
 				ts.Defer(srv.Close)
 			},
+			// find-files recursively lists files under a directory, like `find -type f` on Linux.
+			// It prints slash-separated paths relative to the root working directory of the testscript run,
+			// for the sake of avoiding verbose and non-deterministic absolute paths.
+			"find-files": func(ts *testscript.TestScript, neg bool, args []string) {
+				if neg || len(args) == 0 {
+					ts.Fatalf("usage: find-files args...")
+				}
+				out := ts.Stdout()
+				workdir := ts.Getenv("WORK")
+				for _, arg := range args {
+					err := filepath.WalkDir(arg, func(path string, d fs.DirEntry, err error) error {
+						if err != nil {
+							return err
+						}
+						if d.Type().IsRegular() {
+							rel, err := filepath.Rel(workdir, path)
+							ts.Check(err)
+							fmt.Fprintln(out, filepath.ToSlash(rel))
+						}
+						return nil
+					})
+					ts.Check(err)
+				}
+			},
 		},
 		Setup: func(e *testscript.Env) error {
 			// If a testscript loads CUE packages but forgot to set up a cue.mod,

cmd/cue/cmd/testdata/script/modtidy_initial.txtar

@@ -13,6 +13,12 @@ cmp stdout want-stdout
 
 # Check that the tidy check succeeds
 exec cue mod tidy --check
+
+# Check what the structure of CUE_CACHE_DIR looks like after fetching modules.
+find-files ${CUE_CACHE_DIR}
+cmp stdout cue-cache-dir.files
+# Unused dependencies should not have their entire source downloaded or extracted.
+! stdout 'unused\.com.*\.zip$'
 -- want-module --
 module: "main.org@v0"
 language: {
@@ -54,6 +60,29 @@ import "example.com@v0:main"
 
 main
 
+-- cue-cache-dir.files --
+.tmp/cache/[email protected]/bar/x.cue
+.tmp/cache/[email protected]/cue.mod/module.cue
+.tmp/cache/[email protected]/baz.cue
+.tmp/cache/[email protected]/cue.mod/module.cue
+.tmp/cache/cache/download/bar.com/@v/v0.5.0.lock
+.tmp/cache/cache/download/bar.com/@v/v0.5.0.mod
+.tmp/cache/cache/download/bar.com/@v/v0.5.0.zip
+.tmp/cache/cache/download/baz.org/@v/v0.10.1.lock
+.tmp/cache/cache/download/baz.org/@v/v0.10.1.mod
+.tmp/cache/cache/download/baz.org/@v/v0.10.1.zip
+.tmp/cache/cache/download/example.com/@v/v0.0.1.lock
+.tmp/cache/cache/download/example.com/@v/v0.0.1.mod
+.tmp/cache/cache/download/example.com/@v/v0.0.1.zip
+.tmp/cache/cache/download/foo.com/bar/hello/@v/v0.2.3.lock
+.tmp/cache/cache/download/foo.com/bar/hello/@v/v0.2.3.mod
+.tmp/cache/cache/download/foo.com/bar/hello/@v/v0.2.3.zip
+.tmp/cache/cache/download/unused.com/@v/v0.2.4.lock
+.tmp/cache/cache/download/unused.com/@v/v0.2.4.mod
+.tmp/cache/[email protected]/cue.mod/module.cue
+.tmp/cache/[email protected]/top.cue
+.tmp/cache/foo.com/bar/[email protected]/cue.mod/module.cue
+.tmp/cache/foo.com/bar/[email protected]/x.cue
 -- _registry/example.com_v0.0.1/cue.mod/module.cue --
 module: "example.com@v0"
 language: version: "v0.8.0"