diagnostics: move diagnostic printing to a new package

This is a refactor, which should (in theory) not change the behavior of
the compiler. But since this is a pretty large change, there is a chance
there will be some regressions. For that reason, the previous commits
added a bunch of tests to make sure most error messages will not be
changed due to this refactor.

diagnostics/diagnostics.go

@@ -0,0 +1,196 @@
+// Package diagnostics formats compiler errors and prints them in a consistent
+// way.
+package diagnostics
+
+import (
+	"bytes"
+	"fmt"
+	"go/scanner"
+	"go/token"
+	"go/types"
+	"io"
+	"path/filepath"
+	"strings"
+
+	"github.com/tinygo-org/tinygo/builder"
+	"github.com/tinygo-org/tinygo/goenv"
+	"github.com/tinygo-org/tinygo/interp"
+	"github.com/tinygo-org/tinygo/loader"
+)
+
+// A single diagnostic.
+type Diagnostic struct {
+	Pos token.Position
+	Msg string
+}
+
+// One or multiple errors of a particular package.
+// It can also represent whole-program errors (like linker errors) that can't
+// easily be connected to a single package.
+type PackageDiagnostic struct {
+	ImportPath  string // the same ImportPath as in `go list -json`
+	Diagnostics []Diagnostic
+}
+
+// Diagnostics of a whole program. This can include errors belonging to multiple
+// packages, or just a single package.
+type ProgramDiagnostic []PackageDiagnostic
+
+// CreateDiagnostics reads the underlying errors in the error object and creates
+// a set of diagnostics that's sorted and can be readily printed.
+func CreateDiagnostics(err error) ProgramDiagnostic {
+	if err == nil {
+		return nil
+	}
+	switch err := err.(type) {
+	case *builder.MultiError:
+		var diags ProgramDiagnostic
+		for _, err := range err.Errs {
+			diags = append(diags, createPackageDiagnostic(err))
+		}
+		return diags
+	default:
+		return ProgramDiagnostic{
+			createPackageDiagnostic(err),
+		}
+	}
+}
+
+// Create diagnostics for a single package (though, in practice, it may also be
+// used for whole-program diagnostics in some cases).
+func createPackageDiagnostic(err error) PackageDiagnostic {
+	var pkgDiag PackageDiagnostic
+	switch err := err.(type) {
+	case loader.Errors:
+		if err.Pkg != nil {
+			pkgDiag.ImportPath = err.Pkg.ImportPath
+		}
+		for _, err := range err.Errs {
+			diags := createDiagnostics(err)
+			pkgDiag.Diagnostics = append(pkgDiag.Diagnostics, diags...)
+		}
+	case *interp.Error:
+		pkgDiag.ImportPath = err.ImportPath
+		w := &bytes.Buffer{}
+		fmt.Fprintln(w, err.Error())
+		if len(err.Inst) != 0 {
+			fmt.Fprintln(w, err.Inst)
+		}
+		if len(err.Traceback) > 0 {
+			fmt.Fprintln(w, "\ntraceback:")
+			for _, line := range err.Traceback {
+				fmt.Fprintln(w, line.Pos.String()+":")
+				fmt.Fprintln(w, line.Inst)
+			}
+		}
+		pkgDiag.Diagnostics = append(pkgDiag.Diagnostics, Diagnostic{
+			Msg: w.String(),
+		})
+	default:
+		pkgDiag.Diagnostics = createDiagnostics(err)
+	}
+	// TODO: sort
+	return pkgDiag
+}
+
+// Extract diagnostics from the given error message and return them as a slice
+// of errors (which in many cases will just be a single diagnostic).
+func createDiagnostics(err error) []Diagnostic {
+	switch err := err.(type) {
+	case types.Error:
+		return []Diagnostic{
+			{
+				Pos: err.Fset.Position(err.Pos),
+				Msg: err.Msg,
+			},
+		}
+	case scanner.Error:
+		return []Diagnostic{
+			{
+				Pos: err.Pos,
+				Msg: err.Msg,
+			},
+		}
+	case scanner.ErrorList:
+		var diags []Diagnostic
+		for _, err := range err {
+			diags = append(diags, createDiagnostics(*err)...)
+		}
+		return diags
+	case loader.Error:
+		if err.Err.Pos.Filename != "" {
+			// Probably a syntax error in a dependency.
+			return createDiagnostics(err.Err)
+		} else {
+			// Probably an "import cycle not allowed" error.
+			buf := &bytes.Buffer{}
+			fmt.Fprintln(buf, "package", err.ImportStack[0])
+			for i := 1; i < len(err.ImportStack); i++ {
+				pkgPath := err.ImportStack[i]
+				if i == len(err.ImportStack)-1 {
+					// last package
+					fmt.Fprintln(buf, "\timports", pkgPath+": "+err.Err.Error())
+				} else {
+					// not the last pacakge
+					fmt.Fprintln(buf, "\timports", pkgPath)
+				}
+			}
+			return []Diagnostic{
+				{Msg: buf.String()},
+			}
+		}
+	default:
+		return []Diagnostic{
+			{Msg: err.Error()},
+		}
+	}
+}
+
+// Write program diagnostics to the given writer with 'wd' as the relative
+// working directory.
+func (progDiag ProgramDiagnostic) WriteTo(w io.Writer, wd string) {
+	for _, pkgDiag := range progDiag {
+		pkgDiag.WriteTo(w, wd)
+	}
+}
+
+// Write package diagnostics to the given writer with 'wd' as the relative
+// working directory.
+func (pkgDiag PackageDiagnostic) WriteTo(w io.Writer, wd string) {
+	if pkgDiag.ImportPath != "" {
+		fmt.Fprintln(w, "#", pkgDiag.ImportPath)
+	}
+	for _, diag := range pkgDiag.Diagnostics {
+		diag.WriteTo(w, wd)
+	}
+}
+
+// Write this diagnostic to the given writer with 'wd' as the relative working
+// directory.
+func (diag Diagnostic) WriteTo(w io.Writer, wd string) {
+	if diag.Pos == (token.Position{}) {
+		fmt.Fprintln(w, diag.Msg)
+		return
+	}
+	pos := diag.Pos // make a copy
+	if !strings.HasPrefix(pos.Filename, filepath.Join(goenv.Get("GOROOT"), "src")) && !strings.HasPrefix(pos.Filename, filepath.Join(goenv.Get("TINYGOROOT"), "src")) {
+		// This file is not from the standard library (either the GOROOT or the
+		// TINYGOROOT). Make the path relative, for easier reading.  Ignore any
+		// errors in the process (falling back to the absolute path).
+		pos.Filename = tryToMakePathRelative(pos.Filename, wd)
+	}
+	fmt.Fprintf(w, "%s: %s\n", pos, diag.Msg)
+}
+
+// try to make the path relative to the current working directory. If any error
+// occurs, this error is ignored and the absolute path is returned instead.
+func tryToMakePathRelative(dir, wd string) string {
+	if wd == "" {
+		return dir // working directory not found
+	}
+	relpath, err := filepath.Rel(wd, dir)
+	if err != nil {
+		return dir
+	}
+	return relpath
+}