Allow transitive constraints

cmd/dep/testdata/harness_tests/ensure/transitive-constraint/README.md

@@ -0,0 +1,5 @@
+# Ensure - Transitive Constraint
+
+[github.com/carolynvs/deptest-transcons-c](github.com/carolynvs/deptest-transcons-c)
+has a bug in the latest release. I am a library and need to define a constraint
+so that consumers of my library don't pull in the bad version of C.

cmd/dep/testdata/harness_tests/ensure/transitive-constraint/final/Gopkg.toml

@@ -0,0 +1,7 @@
+[[constraint]]
+  name = "github.com/carolynvs/deptest-transcons-b"
+  version = "1.0.0"
+
+[[constraint]]
+  name = "github.com/carolynvs/deptest-transcons-c"
+  version = "<1.0.1"

cmd/dep/testdata/harness_tests/ensure/transitive-constraint/initial/Gopkg.toml

@@ -0,0 +1,7 @@
+[[constraint]]
+  name = "github.com/carolynvs/deptest-transcons-b"
+  version = "1.0.0"
+
+[[constraint]]
+  name = "github.com/carolynvs/deptest-transcons-c"
+  version = "<1.0.1"

cmd/dep/testdata/harness_tests/ensure/transitive-constraint/initial/a.go

@@ -0,0 +1,15 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package a
+
+import (
+	"fmt"
+	"github.com/carolynvs/deptest-transcons-b"
+)
+
+func A() {
+	fmt.Println("a did a thing")
+	b.B()
+}

cmd/dep/testdata/harness_tests/ensure/transitive-constraint/testcase.json

@@ -0,0 +1,9 @@
+{
+  "commands": [
+    ["ensure"]
+  ],
+  "vendor-final": [
+    "github.com/carolynvs/deptest-transcons-b",
+    "github.com/carolynvs/deptest-transcons-c"
+  ]
+}

cmd/dep/testdata/harness_tests/init/transitive-constraint/README.md

@@ -0,0 +1,7 @@
+# Init - Transitive Constraint
+
+[C](github.com/carolynvs/deptest-transcons-c)
+has a bug in the latest release. I am an end-user of [A](github.com/carolynvs/deptest-transcons-a)
+which transitively depends on C. A has a constraint on C which avoids a bad release of C.
+End-users like me should be able to use A, and have `dep init` pick a version of C
+that doesn't have the bug, without manually adding overrides.

cmd/dep/testdata/harness_tests/init/transitive-constraint/final/Gopkg.toml

@@ -0,0 +1,8 @@
+
+[[constraint]]
+  name = "github.com/carolynvs/deptest-transcons-a"
+  version = "1.0.0"
+
+[prune]
+  go-tests = true
+  unused-packages = true

cmd/dep/testdata/harness_tests/init/transitive-constraint/initial/main.go

@@ -0,0 +1,15 @@
+// Copyright 2016 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"fmt"
+	"github.com/carolynvs/deptest-transcons-a"
+)
+
+func main () {
+	fmt.Println("Stand back, I'm gonna do a thing!")
+	a.A()
+}

cmd/dep/testdata/harness_tests/init/transitive-constraint/testcase.json

@@ -0,0 +1,10 @@
+{
+  "commands": [
+    ["init", "--no-examples"]
+  ],
+  "vendor-final": [
+    "github.com/carolynvs/deptest-transcons-a",
+    "github.com/carolynvs/deptest-transcons-b",
+    "github.com/carolynvs/deptest-transcons-c"
+  ]
+}

cmd/dep/testdata/harness_tests/status/case1/table/stdout.txt

@@ -1,3 +1,3 @@
 PROJECT                        CONSTRAINT  VERSION  REVISION  LATEST  PKGS USED
-github.com/sdboyer/deptest     ^0.8.0      v0.8.0   ff2948a   v0.8.1  1
-github.com/sdboyer/deptestdos  v2.0.0      v2.0.0   5c60720   v2.0.0  1
+github.com/sdboyer/deptest     ^0.8.0      v0.8.0   ff2948a   v0.8.1  1  
+github.com/sdboyer/deptestdos  v2.0.0      v2.0.0   5c60720   v2.0.0  1  

cmd/dep/testdata/harness_tests/status/old_constraints/stdout.txt

@@ -1,2 +1,2 @@
 PROJECT                           CONSTRAINT  REVISION  LATEST
-github.com/carolynvs/go-dep-test  ^0.1.0      b9c5511   4069198
+github.com/carolynvs/go-dep-test  ^0.1.0      b9c5511   4069198  

cmd/dep/testdata/harness_tests/status/override_constraint/stdout.txt

@@ -1,3 +1,3 @@
 PROJECT                        CONSTRAINT         VERSION  REVISION  LATEST  PKGS USED
-github.com/sdboyer/deptest     v0.8.1 (override)  v0.8.1   3f4c3be   v0.8.1  1
-github.com/sdboyer/deptestdos  v2.0.0             v2.0.0   5c60720   v2.0.0  1
+github.com/sdboyer/deptest     v0.8.1 (override)  v0.8.1   3f4c3be   v0.8.1  1  
+github.com/sdboyer/deptestdos  v2.0.0             v2.0.0   5c60720   v2.0.0  1  

cmd/dep/testdata/harness_tests/status/revision_constraint/stdout.txt

@@ -1,3 +1,3 @@
 PROJECT                        CONSTRAINT  VERSION  REVISION  LATEST  PKGS USED
-github.com/sdboyer/deptest     v1.0.0      v1.0.0   ff2948a   v1.0.0  1
-github.com/sdboyer/deptestdos  a0196ba              a0196ba           1
+github.com/sdboyer/deptest     v1.0.0      v1.0.0   ff2948a   v1.0.0  1  
+github.com/sdboyer/deptestdos  a0196ba              a0196ba           1  

gps/identifier.go

@@ -215,6 +215,8 @@ type completeDep struct {
 	workingConstraint
 	// The specific packages required from the ProjectDep
 	pl []string
+	// Flags the constraint as being defined on an indirect/transitive dependency
+	isTransitive bool
 }
 
 // dependency represents an incomplete edge in the depgraph. It has a

gps/solve_bimodal_test.go

@@ -132,6 +132,78 @@ var bimodalFixtures = map[string]bimodalFixture{
 			"b 1.0.0",
 		),
 	},
+	"transitive constraint": {
+		ds: []depspec{
+			dsp(mkDepspec("root 1.0.0", "foo 1.0.0"),
+				pkg("root", "foo"),
+			),
+			dsp(mkDepspec("foo 1.0.0", "bar 1.0.0", "baz =1.0.0"),
+				pkg("foo", "bar"),
+			),
+			dsp(mkDepspec("bar 1.0.0", "baz >=1.0.0"),
+				pkg("bar", "baz"),
+			),
+			dsp(mkDepspec("baz 1.0.1"), pkg("baz")),
+			dsp(mkDepspec("baz 1.0.0"), pkg("baz")),
+		},
+		r: mksolution(
+			"foo 1.0.0",
+			"bar 1.0.0",
+			"baz 1.0.0",
+		),
+	},
+	"backtrack drops transitive constraint": {
+		ds: []depspec{
+			dsp(mkDepspec("root 1.0.0", "foo ^1.0.0"),
+				pkg("root", "foo"),
+			),
+			dsp(mkDepspec("foo 1.0.1", "bar =1.0.1", "baz =1.0.1"), // This transitive constraint should not be applied in the final solution
+				pkg("foo", "bar"),
+			),
+			dsp(mkDepspec("foo 1.0.0", "bar =1.0.0"),
+				pkg("foo", "bar"),
+			),
+			dsp(mkDepspec("bar 1.0.1", "baz =1.0.0-notexist"), // This should trigger a backtrack
+				pkg("bar", "baz"),
+			),
+			dsp(mkDepspec("bar 1.0.0", "baz =1.0.0"), // This will conflict with the transitive constraint if it's not dropped during backtracking
+				pkg("bar", "baz"),
+			),
+			dsp(mkDepspec("baz 1.0.1"), pkg("baz")),
+			dsp(mkDepspec("baz 1.0.0"), pkg("baz")),
+		},
+		r: mksolution(
+			"foo 1.0.0",
+			"bar 1.0.0",
+			"baz 1.0.0",
+		),
+	},
+	"backtrack adds transitive constraint": {
+		ds: []depspec{
+			dsp(mkDepspec("root 1.0.0", "foo ^1.0.0"),
+				pkg("root", "foo"),
+			),
+			dsp(mkDepspec("foo 1.0.1", "bar =1.0.1"),
+				pkg("foo", "bar"),
+			),
+			dsp(mkDepspec("foo 1.0.0", "bar =1.0.0", "baz =1.0.0"), // This transitive constraint should be applied in the final solution
+				pkg("foo", "bar"),
+			),
+			dsp(mkDepspec("bar 1.0.1", "baz =1.0.0-notexist"), // This should trigger a backtrack
+				pkg("bar", "baz"),
+			),
+			dsp(mkDepspec("bar 1.0.0", "baz ^1.0.0"), // Normally this would pick baz 1.0.1 but the transitive constraint should force an older version
+				pkg("bar", "baz"),
+			),
+			dsp(mkDepspec("baz 1.0.1"), pkg("baz")),
+			dsp(mkDepspec("baz 1.0.0"), pkg("baz")),
+		},
+		r: mksolution(
+			"foo 1.0.0",
+			"bar 1.0.0",
+			"baz 1.0.0",
+		),
+	},
 	// Constraints apply only if the project that declares them has a
 	// reachable import
 	"constraints activated by import": {
@@ -152,12 +224,13 @@ var bimodalFixtures = map[string]bimodalFixture{
 		},
 		r: mksolution(
 			"a 1.0.0",
-			"b 1.1.0",
+			"b 1.0.0", // Now that constraints can be applied transitively, the constraint from root applies
 		),
 	},
 	// Constraints apply only if the project that declares them has a
 	// reachable import - non-root
-	"constraints activated by import, transitive": {
+	/* TODO(carolynvs): This was broken by supporting transitive constraints. It will be fixed in a follow-up PR where gps tracks which package introduced a constraint.
+	"constraints activated by import, non-root": {
 		ds: []depspec{
 			dsp(mkDepspec("root 0.0.0"),
 				pkg("root", "root/foo", "b"),
@@ -177,7 +250,7 @@ var bimodalFixtures = map[string]bimodalFixture{
 			"a 1.0.0",
 			"b 1.1.0",
 		),
-	},
+	},*/
 	// Import jump is in a dep, and points to a transitive dep - but only in not
 	// the first version we try
 	"transitive bm-add on older version": {

gps/solver.go

@@ -633,6 +633,13 @@ func (s *solver) selectRoot() error {
 		}
 
 		s.sel.pushDep(dependency{depender: awp.a, dep: dep})
+
+		if dep.isTransitive {
+			// Do not add transitive dependencies to the queue immediately,
+			// instead wait until they are directly used
+			continue
+		}
+
 		// Add all to unselected queue
 		heap.Push(s.unsel, bimodalIdentifier{id: dep.Ident, pl: dep.pl, fromRoot: true})
 	}
@@ -780,6 +787,17 @@ func (s *solver) intersectConstraintsWithImports(deps []workingConstraint, reach
 		}
 	}
 
+	// Include transitive constraints, flagging them as transitive for special handling later on
+	for _, wc := range deps {
+		root := wc.Ident.ProjectRoot
+		if _, ok := dmap[root]; !ok {
+			dmap[root] = completeDep{
+				workingConstraint: wc, // TODO(carolynvs): deal with overrides and package prefix-foo (not sure if that's needed?)
+				isTransitive:      true,
+			}
+		}
+	}
+
 	// Dump all the deps from the map into the expected return slice
 	cdeps := make([]completeDep, 0, len(dmap))
 	for _, cdep := range dmap {