Prevent duplicate instruction appending in generate_prompts

[ccope]

The generate_prompts function appended instructions multiple times when called repeatedly with the same opts object, causing duplicate content in both the instruction string and messages array.

Resolves #2907

Changes

• Instruction file loading (lines 265-273): Added opts._instructions_loaded guard flag to prevent re-reading and re-appending file content. Flag set after file processing regardless of content to avoid redundant I/O.

• Message array insertion (lines 444-447): Added opts._instructions_added_to_messages guard flag to prevent duplicate instruction messages.

Example

local opts = { instructions = "Initial" }

-- Without guards (old behavior):
generate_prompts(opts)  -- instructions: "Initial\nFile content"
generate_prompts(opts)  -- instructions: "Initial\nFile content\nFile content" ❌

-- With guards (new behavior):
generate_prompts(opts)  -- instructions: "Initial\nFile content"
generate_prompts(opts)  -- instructions: "Initial\nFile content" ✓

Tests

Added two test cases validating no duplication occurs across multiple generate_prompts calls with the same opts object.

Copilot PR from my fork: ccope#1

Original prompt

Problem

The generate_prompts function in lua/avante/llm.lua has two issues where instructions can be appended multiple times if the function is called repeatedly with the same opts object:

1. Lines 265-270: Instructions from the project instruction file are appended to opts.instructions without checking if they've already been added
2. Lines 441-443: The instructions are added to the messages array without checking if they've already been added

This causes duplicate content when generate_prompts is called multiple times with the same options.

Solution

Add guard flags to prevent duplicate appending:

1. Add opts._instructions_loaded flag to track if the instruction file content has been loaded
2. Add opts._instructions_added_to_messages flag to track if instructions have been added to the messages array

Changes Required

In lua/avante/llm.lua, modify the M.generate_prompts function:

Around line 265-270, change:

if instruction_file_path:exists() then
  local lines = Utils.read_file_from_buf_or_disk(instruction_file_path:absolute())
  local instruction_content = lines and table.concat(lines, "\n") or ""

  if instruction_content then opts.instructions = (opts.instructions or "") .. "\n" .. instruction_content end
end

To:

if instruction_file_path:exists() and not opts._instructions_loaded then
  local lines = Utils.read_file_from_buf_or_disk(instruction_file_path:absolute())
  local instruction_content = lines and table.concat(lines, "\n") or ""

  if instruction_content then 
    opts.instructions = (opts.instructions or "") .. "\n" .. instruction_content 
    opts._instructions_loaded = true
  end
end

Around line 441-443, change:

if opts.instructions ~= nil and opts.instructions ~= "" then
  messages = vim.list_extend(messages, { { role = "user", content = opts.instructions } })
end

To:

if opts.instructions ~= nil and opts.instructions ~= "" and not opts._instructions_added_to_messages then
  messages = vim.list_extend(messages, { { role = "user", content = opts.instructions } })
  opts._instructions_added_to_messages = true
end

Expected Outcome

After these changes, the generate_prompts function can be safely called multiple times with the same opts object without duplicating instruction content.

This pull request was created from Copilot chat.

[ccope]

I've been using this change locally for the past couple of days and I've stopped getting warnings about duplicated instructions. I'm not super familiar with this plugin's code though, so I may have missed edge cases in the LLM's output.

[ccope]

Ah this looks like a duplicate of #2884

[github-actions]

This PR is stale because it has been open 14 days with no activity. Remove stale label or comment or this will be closed in 10 days.

[ccope]

Bumping this because it looks like the other PR got closed as stale.