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Bryan C. Mills
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cmd/go/internal/mvs: export a NewBuildListError function
Also factor out BuildListError to a separate file. For #36460 Change-Id: Ibd1143893b09a2bbef659bea1e8c5dd35184a7ef Reviewed-on: https://go-review.googlesource.com/c/go/+/247764 Reviewed-by: Jay Conrod <[email protected]>
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-65
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2 files changed

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lines changed

‎src/cmd/go/internal/mvs/errors.go

Lines changed: 96 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,96 @@
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// Copyright 2020 The Go Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package mvs
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import (
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"fmt"
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"strings"
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"golang.org/x/mod/module"
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)
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// BuildListError decorates an error that occurred gathering requirements
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// while constructing a build list. BuildListError prints the chain
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// of requirements to the module where the error occurred.
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type BuildListError struct {
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Err error
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stack []buildListErrorElem
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}
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type buildListErrorElem struct {
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m module.Version
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// nextReason is the reason this module depends on the next module in the
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// stack. Typically either "requires", or "updating to".
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nextReason string
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}
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// NewBuildListError returns a new BuildListError wrapping an error that
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// occurred at a module found along the given path of requirements and/or
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// upgrades, which must be non-empty.
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//
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// The isUpgrade function reports whether a path step is due to an upgrade.
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// A nil isUpgrade function indicates that none of the path steps are due to upgrades.
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func NewBuildListError(err error, path []module.Version, isUpgrade func(from, to module.Version) bool) *BuildListError {
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stack := make([]buildListErrorElem, 0, len(path))
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for len(path) > 1 {
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reason := "requires"
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if isUpgrade != nil && isUpgrade(path[0], path[1]) {
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reason = "updating to"
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}
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stack = append(stack, buildListErrorElem{
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m: path[0],
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nextReason: reason,
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})
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path = path[1:]
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}
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stack = append(stack, buildListErrorElem{m: path[0]})
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return &BuildListError{
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Err: err,
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stack: stack,
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}
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}
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// Module returns the module where the error occurred. If the module stack
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// is empty, this returns a zero value.
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func (e *BuildListError) Module() module.Version {
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if len(e.stack) == 0 {
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return module.Version{}
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}
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return e.stack[len(e.stack)-1].m
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}
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func (e *BuildListError) Error() string {
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b := &strings.Builder{}
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stack := e.stack
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// Don't print modules at the beginning of the chain without a
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// version. These always seem to be the main module or a
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// synthetic module ("target@").
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for len(stack) > 0 && stack[0].m.Version == "" {
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stack = stack[1:]
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}
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if len(stack) == 0 {
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b.WriteString(e.Err.Error())
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} else {
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for _, elem := range stack[:len(stack)-1] {
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fmt.Fprintf(b, "%s@%s %s\n\t", elem.m.Path, elem.m.Version, elem.nextReason)
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}
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// Ensure that the final module path and version are included as part of the
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// error message.
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m := stack[len(stack)-1].m
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if _, ok := e.Err.(*module.ModuleError); ok {
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// TODO(bcmills): Also ensure that the module path and version match.
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// (Otherwise, we may be reporting an error from a replacement without
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// indicating the replacement path.)
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fmt.Fprintf(b, "%v", e.Err)
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} else {
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fmt.Fprintf(b, "%v", module.VersionError(m, e.Err))
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}
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}
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return b.String()
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}

‎src/cmd/go/internal/mvs/mvs.go

Lines changed: 12 additions & 65 deletions
Original file line numberDiff line numberDiff line change
@@ -9,7 +9,6 @@ package mvs
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import (
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"fmt"
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"sort"
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"strings"
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"sync"
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"sync/atomic"
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@@ -61,59 +60,6 @@ type Reqs interface {
6160
Previous(m module.Version) (module.Version, error)
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}
6362

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// BuildListError decorates an error that occurred gathering requirements
65-
// while constructing a build list. BuildListError prints the chain
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// of requirements to the module where the error occurred.
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type BuildListError struct {
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Err error
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stack []buildListErrorElem
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}
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type buildListErrorElem struct {
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m module.Version
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// nextReason is the reason this module depends on the next module in the
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// stack. Typically either "requires", or "upgraded to".
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nextReason string
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}
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// Module returns the module where the error occurred. If the module stack
81-
// is empty, this returns a zero value.
82-
func (e *BuildListError) Module() module.Version {
83-
if len(e.stack) == 0 {
84-
return module.Version{}
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}
86-
return e.stack[len(e.stack)-1].m
87-
}
88-
89-
func (e *BuildListError) Error() string {
90-
b := &strings.Builder{}
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stack := e.stack
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// Don't print modules at the beginning of the chain without a
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// version. These always seem to be the main module or a
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// synthetic module ("target@").
96-
for len(stack) > 0 && stack[0].m.Version == "" {
97-
stack = stack[1:]
98-
}
99-
100-
if len(stack) == 0 {
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b.WriteString(e.Err.Error())
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} else {
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for _, elem := range stack[:len(stack)-1] {
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fmt.Fprintf(b, "%s@%s %s\n\t", elem.m.Path, elem.m.Version, elem.nextReason)
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}
106-
// Ensure that the final module path and version are included as part of the
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// error message.
108-
if _, ok := e.Err.(*module.ModuleError); ok {
109-
fmt.Fprintf(b, "%v", e.Err)
110-
} else {
111-
fmt.Fprintf(b, "%v", module.VersionError(stack[len(stack)-1].m, e.Err))
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}
113-
}
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return b.String()
115-
}
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// BuildList returns the build list for the target module.
11864
//
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// target is the root vertex of a module requirement graph. For cmd/go, this is
@@ -202,29 +148,30 @@ func buildList(target module.Version, reqs Reqs, upgrade func(module.Version) (m
202148
q = q[1:]
203149

204150
if node.err != nil {
205-
// Construct the stack reversed (from the error to the main module),
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pathUpgrade := map[module.Version]module.Version{}
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// Construct the error path reversed (from the error to the main module),
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// then reverse it to obtain the usual order (from the main module to
207155
// the error).
208-
stack := []buildListErrorElem{{m: node.m}}
156+
errPath := []module.Version{node.m}
209157
for n, prev := neededBy[node], node; n != nil; n, prev = neededBy[n], n {
210-
reason := "requires"
211158
if n.upgrade == prev.m {
212-
reason = "updating to"
159+
pathUpgrade[n.m] = prev.m
213160
}
214-
stack = append(stack, buildListErrorElem{m: n.m, nextReason: reason})
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errPath = append(errPath, n.m)
215162
}
216-
i, j := 0, len(stack)-1
163+
i, j := 0, len(errPath)-1
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for i < j {
218-
stack[i], stack[j] = stack[j], stack[i]
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errPath[i], errPath[j] = errPath[j], errPath[i]
219166
i++
220167
j--
221168
}
222169

223-
err := &BuildListError{
224-
Err: node.err,
225-
stack: stack,
170+
isUpgrade := func(from, to module.Version) bool {
171+
return pathUpgrade[from] == to
226172
}
227-
return nil, err
173+
174+
return nil, NewBuildListError(node.err, errPath, isUpgrade)
228175
}
229176

230177
neighbors := node.required

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