Error on name conflicts in re-exports

CHANGELOG.md

@@ -4,7 +4,6 @@
 
 * Adds CLI flag `--strict` to break with an error instead of warnings (#68)
 * Adds CLI flag `--dry-run` to run without file output (#71)
-* Checks package re-exports, giving warning or error on fail (#68)
 * Allows for cross-refs to aliases in modules and structs (#69)
 
 ### Documentation
@@ -16,6 +15,11 @@
 * Don't trim docstrings during extraction and removal of exports section (#60)
 * Fixes broken links when referencing parents or the root package (#62)
 
+### Other
+
+* Checks package re-exports for correct paths (#68)
+* Checks package re-exports for resulting name conflicts (#72)
+
 ## [[v0.6.0]](https://github.com/mlange-42/modo/compare/v0.5.0...v0.6.0)
 
 ### Features

document/exports.go

@@ -2,6 +2,7 @@ package document
 
 import (
 	"bufio"
+	"fmt"
 	"strings"
 )
 
@@ -38,9 +39,7 @@ func (proc *Processor) collectExports(p *Package, elems []string) (bool, error)
 		}
 		for _, ex := range p.exports {
 			if _, ok := proc.allPaths[strings.Join(ex.Long, ".")]; !ok {
-				if err := proc.warnOrError("Unresolved package re-export '%s' in %s", strings.Join(ex.Long, "."), strings.Join(newElems, ".")); err != nil {
-					return anyExports, err
-				}
+				return anyExports, fmt.Errorf("unresolved package re-export '%s' in %s", strings.Join(ex.Long, "."), strings.Join(newElems, "."))
 			}
 		}
 		return anyExports, nil

document/filter.go

@@ -2,13 +2,15 @@ package document
 
 import (
 	"fmt"
+	"strings"
 )
 
 // Filters and re-structures docs for package re-exports.
 //
 // Also collects a lookup, mapping from original to altered cross-refs.
 func (proc *Processor) filterPackages() error {
 	proc.linkExports = map[string]string{}
+	proc.linkExportsReverse = map[string]*exportError{}
 	anyExports, err := proc.collectExports(proc.Docs.Decl, nil)
 	if err != nil {
 		return err
@@ -32,7 +34,35 @@ func (proc *Processor) filterPackages() error {
 	}
 	proc.addLinkExport([]string{proc.Docs.Decl.Name}, []string{proc.Docs.Decl.Name})
 	proc.filterPackage(proc.Docs.Decl, proc.ExportDocs.Decl, nil, nil)
-	return nil
+
+	errs := []*exportError{}
+	for _, expErr := range proc.linkExportsReverse {
+		if len(expErr.OldPaths) > 1 {
+			errs = append(errs, expErr)
+		}
+	}
+	if len(errs) == 0 {
+		return nil
+	}
+	msg := strings.Builder{}
+	msg.WriteString(fmt.Sprintln("Name collisions in package re-exports:"))
+	for _, expErr := range errs {
+		msg.WriteString(fmt.Sprintf(" - %s (", expErr.NewPath))
+		for i, pOld := range expErr.OldPaths {
+			if i > 0 {
+				msg.WriteString(", ")
+			}
+			msg.WriteString(pOld)
+		}
+		msg.WriteString(")\n")
+	}
+
+	return fmt.Errorf("%s", msg.String())
+}
+
+type exportError struct {
+	NewPath  string
+	OldPaths []string
 }
 
 func (proc *Processor) filterPackage(src, rootOut *Package, oldPath, newPath []string) {

document/processor.go

@@ -20,15 +20,16 @@ type Config struct {
 }
 
 type Processor struct {
-	Config      *Config
-	Template    *template.Template
-	Formatter   Formatter
-	Docs        *Docs
-	ExportDocs  *Docs
-	allPaths    map[string]bool
-	linkTargets map[string]elemPath
-	linkExports map[string]string
-	writer      func(file, text string) error
+	Config             *Config
+	Template           *template.Template
+	Formatter          Formatter
+	Docs               *Docs
+	ExportDocs         *Docs
+	allPaths           map[string]bool
+	linkTargets        map[string]elemPath
+	linkExports        map[string]string
+	linkExportsReverse map[string]*exportError
+	writer             func(file, text string) error
 }
 
 func NewProcessor(docs *Docs, f Formatter, t *template.Template, config *Config) *Processor {
@@ -83,7 +84,17 @@ func (proc *Processor) warnOrError(pattern string, args ...any) error {
 }
 
 func (proc *Processor) addLinkExport(oldPath, newPath []string) {
-	proc.linkExports[strings.Join(oldPath, ".")] = strings.Join(newPath, ".")
+	pNew := strings.Join(newPath, ".")
+	pOld := strings.Join(oldPath, ".")
+	if present, ok := proc.linkExportsReverse[pNew]; ok {
+		present.OldPaths = append(present.OldPaths, pOld)
+	} else {
+		proc.linkExportsReverse[pNew] = &exportError{
+			NewPath:  pNew,
+			OldPaths: []string{pOld},
+		}
+	}
+	proc.linkExports[pOld] = pNew
 }
 
 func (proc *Processor) addLinkTarget(elPath, filePath []string, kind string, isSection bool) {