Implement ale.get_filename_mappings in Lua

doc/ale.txt

@@ -4477,6 +4477,7 @@ ale#Escape(str)                                                  *ale#Escape()*
   In all other cases, ALE will call |shellescape|.
 
 
+ale.get_filename_mappings(buffer, name)           *ale.get_filename_mappings()*
 ale#GetFilenameMappings(buffer, name)               *ale#GetFilenameMappings()*
 
   Given a `buffer` and the `name` of either a linter for fixer, return a

lua/ale/init.lua

@@ -114,4 +114,25 @@ ale.env = function(variable_name, value)
     return variable_name .. "=" .. ale.escape(value) .. " "
 end
 
+---Get an array of arrays for mapping paths to and from filesystems for an ALE
+---linter, as configured in the `filename_mappings` setting.
+---
+---The result can be used to instruct ALE how to map between filesystems.
+---@param buffer number The buffer number.
+---@param name string The linter name.
+---@return table mappings An array of arrays for mapping filenames.
+ale.get_filename_mappings = function(buffer, name)
+    local linter_mappings = ale.var(buffer, "filename_mappings")
+
+    if linter_mappings[1] ~= nil then
+        return linter_mappings
+    end
+
+    if linter_mappings[name] == nil then
+        name = "*"
+    end
+
+    return linter_mappings[name] or {}
+end
+
 return ale

test/lua/ale_get_filename_mappings_spec.lua

@@ -0,0 +1,77 @@
+local eq = assert.are.same
+local ale = require("ale")
+
+describe("ale.get_filename_mappings", function()
+    local buffer_map
+
+    setup(function()
+        _G.vim = {
+            api = {
+                nvim_buf_get_var = function(buffer, key)
+                    local buffer_table = buffer_map[buffer] or {}
+                    local value = buffer_table[key]
+
+                    if value == nil then
+                        error(key .. " is missing")
+                    end
+
+                    return value
+                end,
+            },
+            g = {
+            },
+        }
+    end)
+
+    teardown(function()
+        _G.vim = nil
+    end)
+
+    before_each(function()
+        buffer_map = {[42] = {}}
+        _G.vim.g = {}
+    end)
+
+    it("should return the correct mappings for given linters/fixers", function()
+        vim.g.ale_filename_mappings = {
+            a = {{"foo", "bar"}},
+            b = {{"baz", "foo"}},
+        }
+
+        eq({{"foo", "bar"}}, ale.get_filename_mappings(42, "a"))
+        eq({{"baz", "foo"}}, ale.get_filename_mappings(42, "b"))
+        eq({}, ale.get_filename_mappings(42, "c"))
+
+        buffer_map[42].ale_filename_mappings = {b = {{"abc", "xyz"}}}
+
+        eq({}, ale.get_filename_mappings(42, "a"))
+        eq({{"abc", "xyz"}}, ale.get_filename_mappings(42, "b"))
+        eq({}, ale.get_filename_mappings(42, "c"))
+    end)
+
+    it("should return arrays set for use with all tools", function()
+        vim.g.ale_filename_mappings = {{"foo", "bar"}}
+
+        eq({{"foo", "bar"}}, ale.get_filename_mappings(42, "a"))
+        eq({{"foo", "bar"}}, ale.get_filename_mappings(42, ""))
+        eq({{"foo", "bar"}}, ale.get_filename_mappings(42, nil))
+
+        buffer_map[42].ale_filename_mappings = {{"abc", "xyz"}}
+
+        eq({{"abc", "xyz"}}, ale.get_filename_mappings(42, "a"))
+        eq({{"abc", "xyz"}}, ale.get_filename_mappings(42, ""))
+        eq({{"abc", "xyz"}}, ale.get_filename_mappings(42, nil))
+    end)
+
+    it("should let you use * as a fallback", function()
+        vim.g.ale_filename_mappings = {
+            a = {{"foo", "bar"}},
+            ["*"] = {{"abc", "xyz"}},
+        }
+
+        eq({{"foo", "bar"}}, ale.get_filename_mappings(42, "a"))
+        eq({{"abc", "xyz"}}, ale.get_filename_mappings(42, "b"))
+        eq({{"abc", "xyz"}}, ale.get_filename_mappings(42, ""))
+        eq({{"abc", "xyz"}}, ale.get_filename_mappings(42, nil))
+    end)
+end)