move checkdupes into parse (#138)

by putting checkdeps into parse, it gets checked by the parse tests
and it just a cleaner place to put it.

mage/main.go

@@ -293,17 +293,6 @@ func Invoke(inv Invocation) int {
 		return 1
 	}
 
-	hasDupes, names := CheckDupes(info)
-	if hasDupes {
-		log.Println("Build targets must be case insensitive, thus the follow targets conflict:")
-		for _, v := range names {
-			if len(v) > 1 {
-				log.Println("  " + strings.Join(v, ", "))
-			}
-		}
-		return 1
-	}
-
 	main := filepath.Join(inv.Dir, mainfile)
 	if err := GenerateMainfile(main, info); err != nil {
 		log.Println("Error:", err)
@@ -331,24 +320,6 @@ func Invoke(inv Invocation) int {
 	return RunCompiled(inv, exePath)
 }
 
-// CheckDupes checks a package for duplicate target names.
-func CheckDupes(info *parse.PkgInfo) (hasDupes bool, names map[string][]string) {
-	names = map[string][]string{}
-	lowers := map[string]bool{}
-	for _, f := range info.Funcs {
-		low := strings.ToLower(f.Name)
-		if f.Receiver != "" {
-			low = strings.ToLower(f.Receiver) + ":" + low
-		}
-		if lowers[low] {
-			hasDupes = true
-		}
-		lowers[low] = true
-		names[low] = append(names[low], f.Name)
-	}
-	return hasDupes, names
-}
-
 type data struct {
 	Description  string
 	Funcs        []parse.Function

mg/deps.go

@@ -119,7 +119,10 @@ func checkFns(fns []interface{}) {
 	}
 }
 
-// Deps runs the given functions with the default runtime context
+// Deps runs the given functions in parallel, exactly once.  This is a way to
+// build up a tree of dependencies with each dependency defining its own
+// dependencies.  Functions must have the same signature as a Mage target, i.e.
+// optional context argument, optional error return.
 func Deps(fns ...interface{}) {
 	CtxDeps(context.Background(), fns...)
 }

parse/parse.go

@@ -1,6 +1,7 @@
 package parse
 
 import (
+	"errors"
 	"fmt"
 	"go/ast"
 	"go/build"
@@ -16,6 +17,8 @@ import (
 	mgTypes "github.com/magefile/mage/types"
 )
 
+// PkgInfo contains inforamtion about a package of files according to mage's
+// parsing rules.
 type PkgInfo struct {
 	Description      string
 	Funcs            []Function
@@ -156,12 +159,41 @@ typeloop:
 		}
 	}
 
+	hasDupes, names := checkDupes(pi)
+	if hasDupes {
+		msg := "Build targets must be case insensitive, thus the following targets conflict:\n"
+		for _, v := range names {
+			if len(v) > 1 {
+				msg += "  " + strings.Join(v, ", ") + "\n"
+			}
+		}
+		return nil, errors.New(msg)
+	}
+
 	setDefault(p, pi, info)
 	setAliases(p, pi, info)
 
 	return pi, nil
 }
 
+// checkDupes checks a package for duplicate target names.
+func checkDupes(info *PkgInfo) (hasDupes bool, names map[string][]string) {
+	names = map[string][]string{}
+	lowers := map[string]bool{}
+	for _, f := range info.Funcs {
+		low := strings.ToLower(f.Name)
+		if f.Receiver != "" {
+			low = strings.ToLower(f.Receiver) + ":" + low
+		}
+		if lowers[low] {
+			hasDupes = true
+		}
+		lowers[low] = true
+		names[low] = append(names[low], f.Name)
+	}
+	return hasDupes, names
+}
+
 // sanitizeSynopsis sanitizes function Doc to create a summary.
 func sanitizeSynopsis(f *doc.Func) string {
 	synopsis := doc.Synopsis(f.Doc)