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