xls_doc/docs/superpowers/specs/2026-06-18-docfill-mvp-design.md

Docfill MVP Design

Goal

Build the smallest local Go command-line tool that a digital employee can call to fill Word or Excel templates from Excel or SQLite data.

MVP Scope

• Input data: .xlsx table or SQLite query result.
• Template files: .docx or .xlsx.
• Placeholder syntax: {{column_name}}.
• Output: one generated file per input row.
• Invocation: docfill run --config task.json.

Explicit Non-Goals

• No web UI.
• No permission system.
• No workflow engine.
• No template designer.
• No direct business-system integration.
• No AI guessing of fields.
• No complex Word layout manipulation.

Config Shape

{
  "data": {
    "type": "excel",
    "path": "./data.xlsx",
    "sheet": "Sheet1"
  },
  "template": {
    "path": "./template.docx"
  },
  "output": {
    "path": "./out/report_{{name}}_{{_row}}.docx"
  }
}

For SQLite, data uses type: "sqlite" and query.

Constraints

• Keep the implementation boring and inspectable.
• Infer template behavior from file extension.
• Treat Excel first row or SQL column names as placeholder keys.
• If a Word placeholder is split across Word XML runs, MVP may not replace it; users should type placeholders as plain contiguous text.