mod/modfile: add ModuleForImportPath

This makes it straightforward to resolve modules and default major
versions for packages without consulting a registry or invoking any of
the code inside internal/mod. This is valid to do for packages that
are part of the current dependency graph as long as the module is
tidy, because the tidy algorithm guarantees that all dependency
modules are present in the module.cue file.

Signed-off-by: Roger Peppe <[email protected]>
Change-Id: Ia0d86b335e2c1f2963e75f7901322fb55a842643
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1207985
Reviewed-by: Daniel Martí <[email protected]>
TryBot-Result: CUEcueckoo <[email protected]>
Unity-Result: CUE porcuepine <[email protected]>

Author: rogpeppe

mod/modfile/modfile.go

@@ -22,6 +22,7 @@ package modfile
 import (
 	_ "embed"
 	"fmt"
+	"path"
 	"slices"
 	"strings"
 	"sync"
@@ -53,12 +54,13 @@ type File struct {
 	// Use the [File.QualifiedModule] method to obtain a module
 	// path that's always qualified. See also the
 	// [File.ModulePath] and [File.MajorVersion] methods.
-	Module   string                    `json:"module"`
-	Language *Language                 `json:"language,omitempty"`
-	Source   *Source                   `json:"source,omitempty"`
-	Deps     map[string]*Dep           `json:"deps,omitempty"`
-	Custom   map[string]map[string]any `json:"custom,omitempty"`
-	versions []module.Version
+	Module          string                    `json:"module"`
+	Language        *Language                 `json:"language,omitempty"`
+	Source          *Source                   `json:"source,omitempty"`
+	Deps            map[string]*Dep           `json:"deps,omitempty"`
+	Custom          map[string]map[string]any `json:"custom,omitempty"`
+	versions        []module.Version
+	versionByModule map[string]module.Version
 	// defaultMajorVersions maps from module base path to the
 	// major version default for that path.
 	defaultMajorVersions map[string]string
@@ -463,6 +465,7 @@ func parse(modfile []byte, filename string, strict bool) (*File, error) {
 			return nil, fmt.Errorf("language version %v in %s is not canonical", vers, filename)
 		}
 	}
+	mf.versionByModule = make(map[string]module.Version)
 	var versions []module.Version
 	defaultMajorVersions := make(map[string]string)
 	if mainPath != "" {
@@ -486,8 +489,17 @@ func parse(modfile []byte, filename string, strict bool) (*File, error) {
 			}
 			defaultMajorVersions[mp] = semver.Major(vers.Version())
 		}
+		mf.versionByModule[vers.Path()] = vers
+	}
+	if mainPath != "" {
+		// We don't necessarily have a full version for the main module.
+		mainWithMajor := mainPath + "@" + mainMajor
+		mainVersion, err := module.NewVersion(mainWithMajor, "")
+		if err != nil {
+			return nil, err
+		}
+		mf.versionByModule[mainWithMajor] = mainVersion
 	}
-
 	if len(defaultMajorVersions) > 0 {
 		mf.defaultMajorVersions = defaultMajorVersions
 	}
@@ -582,3 +594,27 @@ func (f *File) DepVersions() []module.Version {
 func (f *File) DefaultMajorVersions() map[string]string {
 	return f.defaultMajorVersions
 }
+
+// ModuleForImportPath returns the module that should contain the given
+// import path and reports whether the module was found.
+// It does not check to see if the import path actually exists within the module.
+//
+// It works entirely from information in f, meaning that it does
+// not consult a registry to resolve a package whose module is not
+// mentioned in the file, which means it will not work in general unless
+// the module is tidy (as with `cue mod tidy`).
+func (f *File) ModuleForImportPath(importPath string) (module.Version, bool) {
+	ip := module.ParseImportPath(importPath)
+	for prefix := ip.Path; prefix != "."; prefix = path.Dir(prefix) {
+		pkgVersion := ip.Version
+		if pkgVersion == "" {
+			if pkgVersion = f.defaultMajorVersions[prefix]; pkgVersion == "" {
+				continue
+			}
+		}
+		if mv, ok := f.versionByModule[prefix+"@"+pkgVersion]; ok {
+			return mv, true
+		}
+	}
+	return module.Version{}, false
+}

mod/modfile/modfile_test.go

@@ -27,13 +27,14 @@ import (
 )
 
 var parseTests = []struct {
-	testName     string
-	parse        func(modfile []byte, filename string) (*File, error)
-	data         string
-	wantError    string
-	want         *File
-	wantVersions []module.Version
-	wantDefaults map[string]string
+	testName             string
+	parse                func(modfile []byte, filename string) (*File, error)
+	data                 string
+	wantError            string
+	want                 *File
+	wantVersions         []module.Version
+	wantDefaults         map[string]string
+	wantModVersionForPkg map[string]string
 }{{
 	testName: "NoDeps",
 	parse:    Parse,
@@ -50,6 +51,15 @@ language: version: "v0.8.0-alpha.0"
 	wantDefaults: map[string]string{
 		"foo.com/bar": "v0",
 	},
+	wantModVersionForPkg: map[string]string{
+		"foo.com/bar":              "foo.com/bar@v0",
+		"foo.com/bar@v0":           "foo.com/bar@v0",
+		"foo.com/bar/baz@v0":       "foo.com/bar@v0",
+		"foo.com/bar@v1":           "",
+		"foo.com/bar:hello":        "foo.com/bar@v0",
+		"foo.com/bar/baz:hello":    "foo.com/bar@v0",
+		"foo.com/bar/baz@v0:hello": "foo.com/bar@v0",
+	},
 }, {
 	testName: "WithDeps",
 	parse:    Parse,
@@ -60,6 +70,11 @@ deps: "example.com@v1": {
 	default: true
 	v: "v1.2.3"
 }
+deps: "example.com/other@v1": v: "v1.9.10"
+deps: "example.com/other/more/nested@v2": {
+	v: "v2.9.20"
+	default: true
+}
 deps: "other.com/something@v0": v: "v0.2.3"
 `,
 	want: &File{
@@ -75,12 +90,36 @@ deps: "other.com/something@v0": v: "v0.2.3"
 			"other.com/something@v0": {
 				Version: "v0.2.3",
 			},
+			"example.com/other@v1": {
+				Version: "v1.9.10",
+			},
+			"example.com/other/more/nested@v2": {
+				Version: "v2.9.20",
+				Default: true,
+			},
 		},
 	},
-	wantVersions: parseVersions("[email protected]", "other.com/[email protected]"),
+	wantVersions: parseVersions(
+		"example.com/other/more/[email protected]",
+		"example.com/[email protected]",
+		"[email protected]",
+		"other.com/[email protected]",
+	),
 	wantDefaults: map[string]string{
-		"foo.com/bar": "v0",
-		"example.com": "v1",
+		"example.com/other/more/nested": "v2",
+		"foo.com/bar":                   "v0",
+		"example.com":                   "v1",
+	},
+	wantModVersionForPkg: map[string]string{
+		"example.com":                       "[email protected]",
+		"example.com/x/y@v1":                "[email protected]",
+		"example.com/x/y@v1:x":              "[email protected]",
+		"example.com/other@v1":              "example.com/[email protected]",
+		"example.com/other/p@v1":            "example.com/[email protected]",
+		"example.com/other/more":            "[email protected]",
+		"example.com/other/more@v1":         "example.com/[email protected]",
+		"example.com/other/more/nested":     "example.com/other/more/[email protected]",
+		"example.com/other/more/nested/x:p": "example.com/other/more/[email protected]",
 	},
 }, {
 	testName: "WithSource",
@@ -270,6 +309,12 @@ deps: "example.com": v: "v1.2.3"
 	wantDefaults: map[string]string{
 		"foo.com/bar": "v0",
 	},
+	wantModVersionForPkg: map[string]string{
+		"example.com":          "", // No default major version.
+		"example.com@v1":       "[email protected]",
+		"example.com/x/y@v1":   "[email protected]",
+		"example.com/x/y@v1:x": "[email protected]",
+	},
 }, {
 	testName: "LegacyWithExtraFields",
 	parse:    ParseLegacy,
@@ -445,6 +490,17 @@ func TestParse(t *testing.T) {
 				qt.Assert(t, qt.Equals(f.ModulePath(), f.Module))
 				qt.Assert(t, qt.Equals(f.MajorVersion(), "v0"))
 			}
+			for p, m := range test.wantModVersionForPkg {
+				t.Run("package-"+p, func(t *testing.T) {
+					mv, ok := f.ModuleForImportPath(p)
+					if m == "" {
+						qt.Assert(t, qt.IsFalse(ok), qt.Commentf("got version %v", mv))
+						return
+					}
+					qt.Check(t, qt.IsTrue(ok))
+					qt.Check(t, qt.Equals(mv.String(), m))
+				})
+			}
 		})
 	}
 }