lsp-impact

Files (2)

• SKILL.md
• patterns.md · references/

SKILL.md (first lines)

> Requires the agent-lsp MCP server.

# lsp-impact

Blast-radius analysis for any symbol or file. Discovers all direct references,
callers (via call hierarchy), and type relationships before you touch anything.
Read-only — does not modify any files.

Run this skill **before** lsp-edit-export: impact tells you what exists and how
widespread the change is; lsp-edit-export tells you how to execute the change safely.

**Invocation:**
- **File path** (e.g. `"internal/lsp/client.go"`) → use the File-level entry (Step 0) to surface all exported-symbol impact at once.
- **Symbol name** in dot notation (e.g. `"codec.Encode"`, `"Buffer.Reset"`) → skip Step 0; start at Prerequisites, then Step 1.

---

## Step 0 — File-level entry (when user provides a file path)

Use this shortcut when the user is changing or auditing an entire file rather
than a single symbol. `blast_radius` enumerates all exported symbols in
the file, resolves their references, and returns test callers (with enclosing
test function names) and non-test callers in a single call.

```
mcp__lsp__blast_radius({
  "changed_files": ["/abs/path/to/file.go"],
  "include_transitive": false   // set true to surface second-order callers
})
```

Returns:
- `affected_symbols` — each exported symbol with its reference count
- `test_callers` — test files + enclosing test function names
- `non_test_callers` — production call sites

**Decision after Step 0:**

| Result | Action |
|--------|--------|
| 0 non-test callers | Low blast radius. Proceed with change. |
| Few callers, known files | Medium risk. Update each call site. |
| Many callers across packages | High risk. Consider staged rollout. |
| Want symbol-level detail | Continue to Steps 1–5 for any specific symbol. |

Skip Steps 1–5 if the file-level summary is sufficient.

---

## Prerequisites (for symbol-level Steps 1–5)

If LSP is not yet initialized, call `mcp__lsp__start_lsp` with the workspace
root first.

Check what the server supports before proceeding — `find_callers` and
`type_hierarchy` are optional LSP features not implemented by all servers:

```
mcp__lsp__get_server_capabilities()
```

Note which tools appear in `supported_tools`. Steps 3 and 4 below depend on
this result.

---

## Step 1 — Locate the symbol

Use `go_to_symbol` with the symbol name provided by the user:

```
mcp__lsp__go_to_symbol({
  "symbol_path": "Package.SymbolName",
  "workspace_root": "/abs/path"   // optional, narrows scope
})
→ returns: file, line, column (1-indexed)
```

`symbol_path` uses dot notation. For a top-level function `Encode` in package
`codec`, use `"codec.Encode"`. For a method `Reset` on type `Buffer`, use
`"Buffer.Reset"`.

Record the returned `file`, `line`, and `column` — you will pass them to
every subsequent step.

---

## Step 2 — Enumerate all direct references (always available)

Call `find_references` with `include_declaration: false` to find every usage
site across the workspace:

```
mcp__lsp__find_references({
  "file_path": "<file from Step 1>",
  "position_pattern": "func @@SymbolName(",   // adjust prefix for symbol kind
  "include_declaration": false
})
```

Collect all reference locations. Group results by file. Record the total count
and list of files — these feed the Impact Report.

See [references/patterns.md](references/patterns.md) for `position_pattern`
examples by language and symbol kind.

---

## Step 3 — Call hierarchy (callers and callees)

Only if `find_callers` appears in `supported_tools` from Step 0.

```
mcp__lsp__find_callers({
  "file_path": "<file from Step 1>",
  "line": <line from Step 1>,
  "column": <column from Step 1>,
  "direction": "incoming"   // use "both" if callees are also needed
})

From blackwell-systems/agent-lsp, MIT.

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