Code coverage report for core/src/log/message-template.ts

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import {MessageContext} from './message';
 
/**
 * Allows additional context to be added to the message string.
 */
export interface MessageTemplate {
  /**
   * Make a string given the `context`.
   * @param context
   *
   */
  format(context: MessageContext): string;
}
 
/**
 * Adds no additonal context to the message string.
 */
export const rawMessageTemplate: MessageTemplate = {
  /**
   *
   * @param context
   * @returns context.message
   */
  format(context: MessageContext): string {
    return context.message;
  }
};
 
 
/**
 * Format a message using a lazily evaluated template string.
 */
export class TemplateStringMessageTemplate implements MessageTemplate {
  /**
   * Will render logger's fqn and the message.
   */
  static readonly DEFAULT_TEMPLATE = '${ctx.data.fqn || ""}: ${ctx.message || ""}';
  private readonly fmt: Function;
 
  /**
   *
   * @param template a template string. **Backticks are not necessary.**
   */
  constructor(readonly template = TemplateStringMessageTemplate.DEFAULT_TEMPLATE) {
    try {
      this.fmt = new Function('ctx', `return \`${this.template}\`;`);
    } catch (error) {
      console.error('TemplateStringMessageTemplate: Error creating template from `%s`!', this.template, error);
      throw error;
    }
  }
 
 
  format(context: MessageContext): string {
    let result: string;
    try {
      result = this.fmt(context);
    } catch (error) {
      console.error('TemplateStringMessageTemplate: Error formatting %o with template %s', context, this.template, error);
      result = context.message;
    }
    return result;
  }
 
}
 
 
export function templateString(template?: string): MessageTemplate {
  return new TemplateStringMessageTemplate(template);
}