Improve bundle validate output (#1532)

## Changes
This combination of changes allows pretty-printing errors happening
during the "load" and "init" phases, including their locations.

Move to render code into a separate module dedicated to rendering
`diag.Diagnostics` in a human-readable format. This will be used for the
`bundle deploy` command.

Preserve the "bundle" value if an error occurs in mutators. Rewrite the
go templates to handle the case when the bundle isn't yet loaded if an
error occurs during loading, that is possible now.

Improve rendering for errors and warnings:
- don't render empty locations
- render "details" for errors if they exist

Add `root.ErrAlreadyPrinted` indicating that the error was already
printed, and the CLI entry point shouldn't print it again.

## Tests
Add tests for output, that are especially handy to detect extra newlines

bundle/render/render_text_output.go

@@ -0,0 +1,176 @@
+package render
+
+import (
+	"fmt"
+	"io"
+	"path/filepath"
+	"strings"
+	"text/template"
+
+	"github.com/databricks/cli/bundle"
+	"github.com/databricks/cli/libs/diag"
+	"github.com/databricks/databricks-sdk-go/service/iam"
+	"github.com/fatih/color"
+)
+
+var renderFuncMap = template.FuncMap{
+	"red":     color.RedString,
+	"green":   color.GreenString,
+	"blue":    color.BlueString,
+	"yellow":  color.YellowString,
+	"magenta": color.MagentaString,
+	"cyan":    color.CyanString,
+	"bold": func(format string, a ...interface{}) string {
+		return color.New(color.Bold).Sprintf(format, a...)
+	},
+	"italic": func(format string, a ...interface{}) string {
+		return color.New(color.Italic).Sprintf(format, a...)
+	},
+}
+
+const errorTemplate = `{{ "Error" | red }}: {{ .Summary }}
+{{- if .Path.String }}
+  {{ "at " }}{{ .Path.String | green }}
+{{- end }}
+{{- if .Location.File }}
+  {{ "in " }}{{ .Location.String | cyan }}
+{{- end }}
+{{- if .Detail }}
+
+{{ .Detail }}
+{{- end }}
+
+`
+
+const warningTemplate = `{{ "Warning" | yellow }}: {{ .Summary }}
+{{- if .Path.String }}
+  {{ "at " }}{{ .Path.String | green }}
+{{- end }}
+{{- if .Location.File }}
+  {{ "in " }}{{ .Location.String | cyan }}
+{{- end }}
+{{- if .Detail }}
+
+{{ .Detail }}
+{{- end }}
+
+`
+
+const summaryTemplate = `{{- if .Name -}}
+Name: {{ .Name | bold }}
+{{- if .Target }}
+Target: {{ .Target | bold }}
+{{- end }}
+{{- if or .User .Host .Path }}
+Workspace:
+{{- if .Host }}
+  Host: {{ .Host | bold }}
+{{- end }}
+{{- if .User }}
+  User: {{ .User | bold }}
+{{- end }}
+{{- if .Path }}
+  Path: {{ .Path | bold }}
+{{- end }}
+{{- end }}
+
+{{ end -}}
+
+{{ .Trailer }}
+`
+
+func pluralize(n int, singular, plural string) string {
+	if n == 1 {
+		return fmt.Sprintf("%d %s", n, singular)
+	}
+	return fmt.Sprintf("%d %s", n, plural)
+}
+
+func buildTrailer(diags diag.Diagnostics) string {
+	parts := []string{}
+	if errors := len(diags.Filter(diag.Error)); errors > 0 {
+		parts = append(parts, color.RedString(pluralize(errors, "error", "errors")))
+	}
+	if warnings := len(diags.Filter(diag.Warning)); warnings > 0 {
+		parts = append(parts, color.YellowString(pluralize(warnings, "warning", "warnings")))
+	}
+	if len(parts) > 0 {
+		return fmt.Sprintf("Found %s", strings.Join(parts, " and "))
+	} else {
+		return color.GreenString("Validation OK!")
+	}
+}
+
+func renderSummaryTemplate(out io.Writer, b *bundle.Bundle, diags diag.Diagnostics) error {
+	if b == nil {
+		return renderSummaryTemplate(out, &bundle.Bundle{}, diags)
+	}
+
+	var currentUser = &iam.User{}
+
+	if b.Config.Workspace.CurrentUser != nil {
+		if b.Config.Workspace.CurrentUser.User != nil {
+			currentUser = b.Config.Workspace.CurrentUser.User
+		}
+	}
+
+	t := template.Must(template.New("summary").Funcs(renderFuncMap).Parse(summaryTemplate))
+	err := t.Execute(out, map[string]any{
+		"Name":    b.Config.Bundle.Name,
+		"Target":  b.Config.Bundle.Target,
+		"User":    currentUser.UserName,
+		"Path":    b.Config.Workspace.RootPath,
+		"Host":    b.Config.Workspace.Host,
+		"Trailer": buildTrailer(diags),
+	})
+
+	return err
+}
+
+func renderDiagnostics(out io.Writer, b *bundle.Bundle, diags diag.Diagnostics) error {
+	errorT := template.Must(template.New("error").Funcs(renderFuncMap).Parse(errorTemplate))
+	warningT := template.Must(template.New("warning").Funcs(renderFuncMap).Parse(warningTemplate))
+
+	// Print errors and warnings.
+	for _, d := range diags {
+		var t *template.Template
+		switch d.Severity {
+		case diag.Error:
+			t = errorT
+		case diag.Warning:
+			t = warningT
+		}
+
+		// Make file relative to bundle root
+		if d.Location.File != "" {
+			out, err := filepath.Rel(b.RootPath, d.Location.File)
+			// if we can't relativize the path, just use path as-is
+			if err == nil {
+				d.Location.File = out
+			}
+		}
+
+		// Render the diagnostic with the appropriate template.
+		err := t.Execute(out, d)
+		if err != nil {
+			return fmt.Errorf("failed to render template: %w", err)
+		}
+	}
+
+	return nil
+}
+
+// RenderTextOutput renders the diagnostics in a human-readable format.
+func RenderTextOutput(out io.Writer, b *bundle.Bundle, diags diag.Diagnostics) error {
+	err := renderDiagnostics(out, b, diags)
+	if err != nil {
+		return fmt.Errorf("failed to render diagnostics: %w", err)
+	}
+
+	err = renderSummaryTemplate(out, b, diags)
+	if err != nil {
+		return fmt.Errorf("failed to render summary: %w", err)
+	}
+
+	return nil
+}