mvs.go

Documentation: cmd/go/internal/modload

     1  // Copyright 2020 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package modload
     6  
     7  import (
     8  	"context"
     9  	"errors"
    10  	"os"
    11  	"sort"
    12  
    13  	"cmd/go/internal/modfetch"
    14  
    15  	"golang.org/x/mod/module"
    16  	"golang.org/x/mod/semver"
    17  )
    18  
    19  // cmpVersion implements the comparison for versions in the module loader.
    20  //
    21  // It is consistent with semver.Compare except that as a special case,
    22  // the version "" is considered higher than all other versions.
    23  // The main module (also known as the target) has no version and must be chosen
    24  // over other versions of the same module in the module dependency graph.
    25  func cmpVersion(v1, v2 string) int {
    26  	if v2 == "" {
    27  		if v1 == "" {
    28  			return 0
    29  		}
    30  		return -1
    31  	}
    32  	if v1 == "" {
    33  		return 1
    34  	}
    35  	return semver.Compare(v1, v2)
    36  }
    37  
    38  // mvsReqs implements mvs.Reqs for module semantic versions,
    39  // with any exclusions or replacements applied internally.
    40  type mvsReqs struct {
    41  	roots []module.Version
    42  }
    43  
    44  func (r *mvsReqs) Required(mod module.Version) ([]module.Version, error) {
    45  	if mod == Target {
    46  		// Use the build list as it existed when r was constructed, not the current
    47  		// global build list.
    48  		return r.roots, nil
    49  	}
    50  
    51  	if mod.Version == "none" {
    52  		return nil, nil
    53  	}
    54  
    55  	summary, err := goModSummary(mod)
    56  	if err != nil {
    57  		return nil, err
    58  	}
    59  	return summary.require, nil
    60  }
    61  
    62  // Max returns the maximum of v1 and v2 according to semver.Compare.
    63  //
    64  // As a special case, the version "" is considered higher than all other
    65  // versions. The main module (also known as the target) has no version and must
    66  // be chosen over other versions of the same module in the module dependency
    67  // graph.
    68  func (*mvsReqs) Max(v1, v2 string) string {
    69  	if cmpVersion(v1, v2) < 0 {
    70  		return v2
    71  	}
    72  	return v1
    73  }
    74  
    75  // Upgrade is a no-op, here to implement mvs.Reqs.
    76  // The upgrade logic for go get -u is in ../modget/get.go.
    77  func (*mvsReqs) Upgrade(m module.Version) (module.Version, error) {
    78  	return m, nil
    79  }
    80  
    81  func versions(ctx context.Context, path string, allowed AllowedFunc) ([]string, error) {
    82  	// Note: modfetch.Lookup and repo.Versions are cached,
    83  	// so there's no need for us to add extra caching here.
    84  	var versions []string
    85  	err := modfetch.TryProxies(func(proxy string) error {
    86  		repo, err := lookupRepo(proxy, path)
    87  		if err != nil {
    88  			return err
    89  		}
    90  		allVersions, err := repo.Versions("")
    91  		if err != nil {
    92  			return err
    93  		}
    94  		allowedVersions := make([]string, 0, len(allVersions))
    95  		for _, v := range allVersions {
    96  			if err := allowed(ctx, module.Version{Path: path, Version: v}); err == nil {
    97  				allowedVersions = append(allowedVersions, v)
    98  			} else if !errors.Is(err, ErrDisallowed) {
    99  				return err
   100  			}
   101  		}
   102  		versions = allowedVersions
   103  		return nil
   104  	})
   105  	return versions, err
   106  }
   107  
   108  // previousVersion returns the tagged version of m.Path immediately prior to
   109  // m.Version, or version "none" if no prior version is tagged.
   110  //
   111  // Since the version of Target is not found in the version list,
   112  // it has no previous version.
   113  func previousVersion(m module.Version) (module.Version, error) {
   114  	// TODO(golang.org/issue/38714): thread tracing context through MVS.
   115  
   116  	if m == Target {
   117  		return module.Version{Path: m.Path, Version: "none"}, nil
   118  	}
   119  
   120  	list, err := versions(context.TODO(), m.Path, CheckAllowed)
   121  	if err != nil {
   122  		if errors.Is(err, os.ErrNotExist) {
   123  			return module.Version{Path: m.Path, Version: "none"}, nil
   124  		}
   125  		return module.Version{}, err
   126  	}
   127  	i := sort.Search(len(list), func(i int) bool { return semver.Compare(list[i], m.Version) >= 0 })
   128  	if i > 0 {
   129  		return module.Version{Path: m.Path, Version: list[i-1]}, nil
   130  	}
   131  	return module.Version{Path: m.Path, Version: "none"}, nil
   132  }
   133  
   134  func (*mvsReqs) Previous(m module.Version) (module.Version, error) {
   135  	return previousVersion(m)
   136  }
   137
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