### Initialize Ruby Flymake Backend

Source: https://www.gnu.org/software/emacs/manual/html_node/flymake/An-annotated-example-backend.html

Sets up the required lexical binding and defines the process variable for the Ruby backend.

```elisp
;;; ruby-flymake.el --- A ruby Flymake backend  -*- lexical-binding: t; -*-
(require 'cl-lib)
(defvar-local ruby--flymake-proc nil)
```

--------------------------------

### Flymake Simple Make Initialization Command

Source: https://www.gnu.org/software/emacs/manual/html_node/flymake/Example_002d_002d_002dConfiguring-a-tool-called-via-make.html

Defines the command line arguments for `make` when used with `flymake-proc-simple-make-init`. It sets the base directory, source files, and syntax check mode.

```emacs-lisp
(list "make"
      (list "-s" "-C"
            base-dir
            (concat "CHK_SOURCES=" source)
            "SYNTAX_CHECK_MODE=1"
            "check-syntax"))

```

--------------------------------

### Map Navigation Commands in Flymake Mode

Source: https://www.gnu.org/software/emacs/manual/html_node/flymake/Finding-diagnostics.html

Map `flymake-goto-next-error` and `flymake-goto-prev-error` to M-n and M-p respectively in `flymake-mode` for easier navigation. Add this to your init file.

```emacs-lisp
(define-key flymake-mode-map (kbd "M-n") 'flymake-goto-next-error)
(define-key flymake-mode-map (kbd "M-p") 'flymake-goto-prev-error)

```

--------------------------------

### Define Perl initialization function for Flymake

Source: https://www.gnu.org/software/emacs/manual/html_node/flymake/Example_002d_002d_002dConfiguring-a-tool-called-directly.html

Creates a temporary buffer copy and constructs the command line arguments for the Perl syntax checker.

```elisp
(defun flymake-proc-perl-init ()
  (let* ((temp-file (flymake-proc-init-create-temp-buffer-copy
                     'flymake-proc-create-temp-inplace))
         (local-file (file-relative-name
                      temp-file
                      (file-name-directory buffer-file-name))))
    (list "perl" (list "-wc " local-file))))
```

--------------------------------

### Flymake Proc Configuration Variables

Source: https://www.gnu.org/software/emacs/manual/html_node/flymake/Proc-customization-variables.html

Reference documentation for the customization variables used to configure the legacy Flymake Proc backend.

```APIDOC
## Flymake Proc Configuration Variables

### Description
Variables used to configure the behavior of the legacy Flymake Proc backend.

### Variables
- **flymake-proc-allowed-file-name-masks** (list) - A list of (filename-regexp, init-function, cleanup-function, getfname-function) for configuring syntax check tools.
- **flymake-proc-master-file-dirs** (list) - A list of directories for searching a master file.
- **flymake-proc-get-project-include-dirs-function** (function) - A function used for obtaining a list of project include directories (C/C++ specific).
- **flymake-proc-master-file-count-limit** (integer) - Limit for searching master files.
- **flymake-proc-check-file-limit** (integer) - Limit used when looking for a master file.
- **flymake-proc-err-line-patterns** (list) - Patterns for error/warning messages in the form (regexp file-idx line-idx col-idx err-text-idx).
- **flymake-proc-diagnostic-type-pred** (function/regexp) - A function to classify diagnostic text or a regular expression matching warnings.
- **flymake-proc-compilation-prevents-syntax-check** (boolean) - A flag indicating whether compilation and syntax check of the same file cannot be run simultaneously.
```

--------------------------------

### Register Ruby Flymake Backend

Source: https://www.gnu.org/software/emacs/manual/html_node/flymake/An-annotated-example-backend.html

Hooks the backend into the Ruby mode diagnostic functions.

```elisp
(defun ruby-setup-flymake-backend ()
  (add-hook 'flymake-diagnostic-functions 'ruby-flymake nil t))

(add-hook 'ruby-mode-hook 'ruby-setup-flymake-backend)
```

--------------------------------

### Define syntax check tool configuration format

Source: https://www.gnu.org/software/emacs/manual/html_node/flymake/Adding-support-for-a-new-syntax-check-tool.html

The structure required for items in the flymake-proc-allowed-file-name-masks list.

```elisp
(filename-regexp, init-function, cleanup-function, getfname-function)
```

--------------------------------

### Flymake Navigation and Display Options

Source: https://www.gnu.org/software/emacs/manual/html_node/flymake/Customizable-variables.html

Variables for controlling navigation between errors and displaying diagnostic summaries.

```APIDOC
## Flymake Navigation and Display Options

### Description
Variables that affect buffer navigation for errors and the display of diagnostic summaries.

### Variables
- `flymake-wrap-around` (boolean) - If non-`nil`, moving to errors with `flymake-goto-next-error` and `flymake-goto-prev-error` wraps around buffer boundaries.
- `flymake-show-diagnostics-at-end-of-line` (boolean) - If non-`nil`, show summarized descriptions of diagnostics at the end of the line.
- `flymake-error-eol` (face) - A custom face for summarizing diagnostic error messages.
- `flymake-warning-eol` (face) - A custom face for summarizing diagnostic warning messages.
- `flymake-note-eol` (face) - A custom face for summarizing diagnostic notes.
```

--------------------------------

### GNU FDL Notice with Invariant Sections and Cover Texts

Source: https://www.gnu.org/software/emacs/manual/html_node/flymake/GNU-Free-Documentation-License.html

Use this template to specify Invariant Sections, Front-Cover Texts, and Back-Cover Texts.

```text
    with the Invariant Sections being list their titles, with
    the Front-Cover Texts being list, and with the Back-Cover Texts
    being list.
```

--------------------------------

### Flymake Backend Function Convention

Source: https://www.gnu.org/software/emacs/manual/html_node/flymake/Backend-functions.html

Describes the expected function signature and arguments for Flymake backend functions.

```APIDOC
## Flymake Backend Function Convention

### Description
Flymake backends are Lisp functions that diagnose buffer contents for problems and report them to Flymake. They must adhere to a specific function calling convention.

### Method
N/A (Lisp function hook)

### Endpoint
N/A (Hook: `flymake-diagnostic-functions`)

### Parameters
#### Function Arguments
- **report-fn** (callback function) - Required - A callback function to report diagnostics to Flymake.
- **keyword-value pairs** (arbitrary) - Optional - Flymake may pass keyword-value pairs such as `:recent-changes`, `:changes-start`, and `:changes-end`.
  - **:recent-changes** (list) - Optional - A list of recent changes in the buffer since the last call. Each element is `(beg end text)`.
  - **:changes-start** (integer) - Optional - The minimum buffer position affected by recent changes. Provided with `:recent-changes`.
  - **:changes-end** (integer) - Optional - The maximum buffer position affected by recent changes. Provided with `:recent-changes`.

### Request Example
N/A (Lisp function call)

### Response
#### Function Return Value
- **Quick return or error signal** - Backends are expected to return quickly or signal an error. Returning successfully means the backend is considered 'running'.

#### Callback Usage
- **report-fn(report-action, [keyword-value pairs])** - Backends call this callback to report diagnostics or errors.
  - **report-action** (list or symbol) - Required - Can be a list of diagnostic objects or the symbol `:panic`.
  - **keyword-value pairs** (list) - Optional - Keyword arguments for reporting, such as `:explanation`, `:force`, `:region`.
    - **:explanation** (string) - Optional - User-readable details of the situation.
    - **:force** (boolean) - Optional - Suggests Flymake consider the report even if unexpected.
    - **:region** (cons) - Optional - A cons cell `(beg . end)` indicating the report's applicable region.
```

--------------------------------

### Register Perl file extension in Flymake

Source: https://www.gnu.org/software/emacs/manual/html_node/flymake/Example_002d_002d_002dConfiguring-a-tool-called-directly.html

Adds a new entry to flymake-proc-allowed-file-name-masks to associate .pl files with the Perl initialization function.

```elisp
(setq flymake-proc-allowed-file-name-masks
      (cons '(".+\\.pl$"
              flymake-proc-perl-init
              flymake-proc-simple-cleanup
              flymake-proc-get-real-file-name)
            flymake-proc-allowed-file-name-masks))
```

--------------------------------

### Standard GNU FDL License Notice

Source: https://www.gnu.org/software/emacs/manual/html_node/flymake/GNU-Free-Documentation-License.html

Use this notice for documents without Invariant Sections or Cover Texts.

```text
  Copyright (C)  year  your name.
  Permission is granted to copy, distribute and/or modify this document
  under the terms of the GNU Free Documentation License, Version 1.3
  or any later version published by the Free Software Foundation;
  with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
  Texts.  A copy of the license is included in the section entitled ``GNU
  Free Documentation License''.
```

--------------------------------

### Flymake Error Highlighting and Indicators

Source: https://www.gnu.org/software/emacs/manual/html_node/flymake/Customizable-variables.html

Variables for customizing how errors, warnings, and notes are displayed.

```APIDOC
## Flymake Error Highlighting and Indicators

### Description
Variables that control the visual representation of syntax errors, warnings, and notes.

### Variables
- `flymake-error` (face) - A custom face for highlighting regions for which an error has been reported.
- `flymake-warning` (face) - A custom face for highlighting regions for which a warning has been reported.
- `flymake-note` (face) - A custom face for highlighting regions for which a note has been reported.
- `flymake-indicator-type` (symbol) - The indicator type which Flymake should use to indicate lines with errors or warnings. Can be `fringes` or `margins`.
- `flymake-error-bitmap` (bitmap) - A bitmap used in the fringe to mark lines for which an error has been reported.
- `flymake-warning-bitmap` (bitmap) - A bitmap used in the fringe to mark lines for which a warning has been reported.
- `flymake-fringe-indicator-position` (symbol) - Which fringe (if any) should show the warning/error bitmaps.
- `flymake-margin-indicators-string` (string) - Specifies the string and face to use for the margin indicators, for each error type.
- `flymake-margin-indicator-position` (symbol) - Which margin (if any) should show the warning/error strings.
- `flymake-autoresize-margins` (boolean) - If non-`nil`, Flymake will resize the margins when `flymake-mode` is turned on or off. Only relevant if `flymake-indicator-type` is set to `margins`.
```

--------------------------------

### Define Ruby Flymake Backend Function

Source: https://www.gnu.org/software/emacs/manual/html_node/flymake/An-annotated-example-backend.html

Implements the main backend function to check Ruby files, managing process lifecycle and diagnostic reporting.

```elisp
(defun ruby-flymake (report-fn &rest _args)
  ;; Not having a ruby interpreter is a serious problem which should cause
  ;; the backend to disable itself, so an error is signaled.
  ;;
  (unless (executable-find
           "ruby") (error "Cannot find a suitable ruby"))
  ;; If a live process launched in an earlier check was found, that
  ;; process is killed.  When that process's sentinel eventually runs,
  ;; it will notice its obsoletion, since it have since reset
  ;; `ruby-flymake-proc' to a different value
  ;;
  (when (process-live-p ruby--flymake-proc)
    (kill-process ruby--flymake-proc))
```

```elisp
  ;; Save the current buffer, the narrowing restriction, remove any
  ;; narrowing restriction.
  ;;
  (let ((source (current-buffer)))
    (save-restriction
      (widen)
      ;; Reset the `ruby--flymake-proc' process to a new process
      ;; calling the ruby tool.
      ;;
      (setq
       ruby--flymake-proc
       (make-process
        :name "ruby-flymake" :noquery t :connection-type 'pipe
        ;; Make output go to a temporary buffer.
        ;;
        :buffer (generate-new-buffer " *ruby-flymake*")
        :command '("ruby" "-w" "-c")
        :sentinel
        (lambda (proc _event)
          ;; Check that the process has indeed exited, as it might
          ;; be simply suspended.
          ;;
          (when (memq (process-status proc) '(exit signal))
            (unwind-protect
                ;; Only proceed if `proc' is the same as
                ;; `ruby--flymake-proc', which indicates that
                ;; `proc' is not an obsolete process.
                ;;
                (if (with-current-buffer source (eq proc ruby--flymake-proc))
                    (with-current-buffer (process-buffer proc)
                      (goto-char (point-min))
                      ;; Parse the output buffer for diagnostic's
                      ;; messages and locations, collect them in a list
                      ;; of objects, and call `report-fn'.
                      ;;
                      (cl-loop
                       while (search-forward-regexp
                              "^\\(?:.*.rb\\|-\\):\\([0-9]+\\): \\(.*\\)$"
                              nil t)
                       for msg = (match-string 2)
                       for (beg . end) = (flymake-diag-region
                                          source
                                          (string-to-number (match-string 1)))
                       for type = (if (string-match "^warning" msg)
                                      :warning
                                    :error)
                       when (and beg end)
                       collect (flymake-make-diagnostic source
                                                        beg
                                                        end
                                                        type
                                                        msg)
                       into diags
                       finally (funcall report-fn diags)))
                  (flymake-log :warning "Canceling obsolete check %s"
                               proc))
              ;; Cleanup the temporary buffer used to hold the
              ;; check's output.
              ;;
              (kill-buffer (process-buffer proc)))))))
      ;; Send the buffer contents to the process's stdin, followed by
      ;; an EOF.
      ;;
      (process-send-region ruby--flymake-proc (point-min) (point-max))
      (process-send-eof ruby--flymake-proc))))
```

--------------------------------

### Restore Original Look for :note Diagnostics

Source: https://www.gnu.org/software/emacs/manual/html_node/flymake/Flymake-error-types.html

Resets the 'flymake-overlay-control' property for :note diagnostics to an empty alist, restoring its original appearance settings.

```Emacs Lisp
(put :note 'flymake-overlay-control '())
```

--------------------------------

### Flymake Syntax Check Behavior

Source: https://www.gnu.org/software/emacs/manual/html_node/flymake/Customizable-variables.html

Variables that control when and how syntax checks are initiated.

```APIDOC
## Flymake Syntax Check Behavior

### Description
Variables that determine the automatic triggering and timing of syntax checks.

### Variables
- `flymake-no-changes-timeout` (integer) - If any changes are made to the buffer, syntax check is automatically started after this many seconds, unless the user makes another change, which resets the timer.
- `flymake-start-on-flymake-mode` (boolean) - A boolean flag indicating whether to start syntax check immediately after enabling `flymake-mode`.
- `flymake-start-on-save-buffer` (boolean) - A boolean flag indicating whether to start syntax check after saving the buffer.
```

--------------------------------

### Configure Perl error line patterns

Source: https://www.gnu.org/software/emacs/manual/html_node/flymake/Example_002d_002d_002dConfiguring-a-tool-called-directly.html

Updates flymake-proc-err-line-patterns to correctly parse Perl error messages.

```elisp
(setq flymake-proc-err-line-patterns
      (cons '("\\(.*\\) at \\([^ \\n]+\\) line \\([0-9]+\\)[,.\\n]"
              2 3 nil 1)
            flymake-proc-err-line-patterns))
```

--------------------------------

### Create Interactive Search Annotation for :warning and :error

Source: https://www.gnu.org/software/emacs/manual/html_node/flymake/Flymake-error-types.html

Defines a function 'my-search-for-message' to search DuckDuckGo for the text of a diagnostic. It then configures :warning and :error types to bind mouse-2 (middle click) to this function, also adding a 'highlight' face.

```Emacs Lisp
(defun my-search-for-message (event)
  (interactive "e")
  (let* ((diags (flymake-diagnostics (posn-point (event-start event))))
         (topmost-diag (car diags)))
    (eww-browse-url
       (concat
        "https://duckduckgo.com/?q="
        (replace-regexp-in-string
          " " "+" (flymake-diagnostic-text topmost-diag))) t)))

(dolist (type '(:warning :error))
  (push '(mouse-face . highlight) (get type 'flymake-overlay-control))
  (push `(keymap . ,(let ((map (make-sparse-keymap)))
                      (define-key map [mouse-2]
                        'my-search-for-message)
                      map))
        (get type 'flymake-overlay-control)))
```

--------------------------------

### Makefile Target for GCC Syntax Check

Source: https://www.gnu.org/software/emacs/manual/html_node/flymake/Example_002d_002d_002dConfiguring-a-tool-called-via-make.html

A sample Makefile target `check-syntax` that uses `gcc` to perform syntax checking on C source files. The `|| true` ensures the build does not fail even if `gcc` reports errors.

```makefile
check-syntax:
	gcc -o /dev/null -S ${CHK_SOURCES} || true

```

--------------------------------

### Make :note Diagnostics Stand Out

Source: https://www.gnu.org/software/emacs/manual/html_node/flymake/Flymake-error-types.html

Adds a 'highlight' face to :note diagnostics to make them more prominent. This modifies the 'flymake-overlay-control' property for the :note symbol.

```Emacs Lisp
(push '(face . highlight) (get :note 'flymake-overlay-control))
```

--------------------------------

### flymake-log

Source: https://www.gnu.org/software/emacs/manual/html_node/flymake/Flymake-utility-functions.html

Logs messages to the Flymake log buffer for troubleshooting purposes. Supports different logging levels.

```APIDOC
## flymake-log

### Description
Log, at level level, the message msg formatted with args. level is passed to `display-warning`, which is used to display the warning in Flymake’s log buffer.

### Macro Signature
flymake-log level msg &optional args

### Parameters
- **level**: The logging level (passed to `display-warning`).
- **msg**: The message string to log.
- **args**: Optional arguments for formatting the message.

### Usage
This macro is intended for backends to record exceptional or erroneous situations into the Flymake log buffer for debugging.
```

--------------------------------

### Makefile Target using Automake COMPILE Variable

Source: https://www.gnu.org/software/emacs/manual/html_node/flymake/Example_002d_002d_002dConfiguring-a-tool-called-via-make.html

An alternative Makefile target `check-syntax` that uses the Automake `COMPILE` variable instead of directly calling `gcc`. This is useful when working with Automake projects.

```makefile
check-syntax:
	$(COMPILE) -o /dev/null -S ${CHK_SOURCES} || true

```

--------------------------------

### Flymake Mode Line Variables

Source: https://www.gnu.org/software/emacs/manual/html_node/flymake/Customizable-variables.html

Variables related to the Flymake mode line indicator and its formatting.

```APIDOC
## Flymake Mode Line Variables

### Description
Variables that control the appearance and content of the Flymake mode line indicator.

### Variables
- `flymake-mode-line-lighter` (string) - The name of the mode. Defaults to ‘Flymake’.
- `flymake-mode-line-format` (string) - Format to use for the Flymake mode line indicator.
- `flymake-mode-line-counter-format` (string) - Mode line construct for formatting Flymake diagnostic counters inside the Flymake mode line indicator.
```

--------------------------------

### Add GCC via Make to Flymake Allowed Masks

Source: https://www.gnu.org/software/emacs/manual/html_node/flymake/Example_002d_002d_002dConfiguring-a-tool-called-via-make.html

Add a new entry to `flymake-proc-allowed-file-name-masks` to enable Flymake's support for C files checked by GCC via Make. This involves specifying the file name mask and the initialization and cleanup functions.

```emacs-lisp
(setq flymake-proc-allowed-file-name-masks
      (cons '(".+\\.c$"
              flymake-proc-simple-make-init
              flymake-proc-simple-cleanup
              flymake-proc-get-real-file-name)
            flymake-proc-allowed-file-name-masks))

```

--------------------------------

### Configure Custom Diagnostic Type :low-priority-note

Source: https://www.gnu.org/software/emacs/manual/html_node/flymake/Flymake-error-types.html

Configures a new diagnostic type ':low-priority-note' to behave like ':note' but without an overlay face. It sets the 'flymake-overlay-control' to '((face . nil))' and 'flymake-category' to 'flymake-note'.

```Emacs Lisp
(put :low-priority-note 'flymake-overlay-control '((face . nil)))
```

```Emacs Lisp
(put :low-priority-note 'flymake-category 'flymake-note)
```

--------------------------------

### flymake-diagnostics

Source: https://www.gnu.org/software/emacs/manual/html_node/flymake/Flymake-utility-functions.html

Retrieves a list of Flymake diagnostic objects within a specified region of the buffer. If no region is specified, it defaults to the entire buffer.

```APIDOC
## flymake-diagnostics

### Description
Get a list of Flymake diagnostics in the region determined by beg and end. If neither beg or end is supplied, use the whole buffer, otherwise if beg is non-`nil` and end is `nil`, consider only diagnostics at beg.

### Function Signature
flymake-diagnostics beg end

### Parameters
- **beg**: The starting position of the region. If `nil`, the whole buffer is considered.
- **end**: The ending position of the region. If `nil` and `beg` is non-`nil`, only diagnostics at `beg` are considered.

### Returns
A list of Flymake diagnostic objects.
```

--------------------------------

### flymake-make-diagnostic

Source: https://www.gnu.org/software/emacs/manual/html_node/flymake/Flymake-utility-functions.html

Creates a Flymake diagnostic object for a specified region of text. This function is fundamental for backends to report detected issues.

```APIDOC
## flymake-make-diagnostic

### Description
Make a Flymake diagnostic for the region of text in locus’s delimited by beg and end. type is a diagnostic symbol, and text is a description of the problem detected in this region.

### Function Signature
flymake-make-diagnostic locus beg end type text &optional data

### Parameters
- **locus**: The buffer object or a string naming a file.
- **beg**: The starting position of the diagnostic region (buffer position or (line . col)).
- **end**: The ending position of the diagnostic region (buffer position or (line . col)).
- **type**: A diagnostic symbol (e.g., error, warning).
- **text**: A description of the problem detected.
- **data**: Optional additional data associated with the diagnostic.

### Related Functions
- `flymake-diagnostic-backend`
- `flymake-diagnostic-buffer`
- `flymake-diagnostic-text`
- `flymake-diagnostic-beg`
- `flymake-diagnostic-end`
- `flymake-diagnostic-type`
- `flymake-diagnostic-data`
- `flymake-diagnostics`
```

--------------------------------

### flymake-diag-region

Source: https://www.gnu.org/software/emacs/manual/html_node/flymake/Flymake-utility-functions.html

Converts line and column numbers into buffer positions (beg . end), which is useful for backends that report diagnostics using line/column information.

```APIDOC
## flymake-diag-region

### Description
Compute buffer’s region (beg . end) corresponding to line and col. If col is `nil`, return a region just for line. Return `nil` if the region is invalid. This function saves match data.

### Function Signature
flymake-diag-region buffer line &optional col

### Parameters
- **buffer**: The buffer to compute the region for.
- **line**: The line number.
- **col**: Optional column number. If `nil`, the region is for the entire line.

### Returns
A cons cell `(beg . end)` representing the buffer region, or `nil` if the region is invalid.
```

--------------------------------

### Remove Face from :note Diagnostics

Source: https://www.gnu.org/software/emacs/manual/html_node/flymake/Flymake-error-types.html

Removes the 'highlight' face from :note diagnostics by pushing '(face . nil) to its 'flymake-overlay-control'. This effectively disables the custom face.

```Emacs Lisp
(push '(face . nil) (get :note 'flymake-overlay-control))
```

=== COMPLETE CONTENT === This response contains all available snippets from this library. No additional content exists. Do not make further requests.