add argument to qmk compile to build compile_commands.json for you

.gitignore

@@ -73,3 +73,7 @@ __pycache__
 
 # prerequisites for updating ChibiOS
 /util/fmpp*
+
+# clangd
+compile_commands.json
+.clangd/

docs/cli_commands.md

@@ -204,6 +204,27 @@ qmk cformat
 qmk cformat -b branch_name
 ```
 
+## `qmk compiledb`
+
+Creates a `compile_commands.json` file.
+
+Does your IDE/editor use a language server but doesn't _quite_ find all the necessary include files? Do you hate red squigglies? Do you wish your editor could figure out `#include QMK_KEYBOARD_H`? You might need a [compilation database](https://clang.llvm.org/docs/JSONCompilationDatabase.html)! The qmk tool can build this for you.
+
+This command needs to know which keyboard and keymap to build. It uses the same configuration options as the `qmk compile` command: arguments, current directory, and config files.
+
+**Example:**
+
+```
+$ cd ~/qmk_firmware/keyboards/gh60/satan/keymaps/colemak
+$ qmk compiledb
+Ψ Making clean
+Ψ Gathering build instructions from make -n gh60/satan:colemak
+Ψ Found 50 compile commands
+Ψ Writing build database to /Users/you/src/qmk_firmware/compile_commands.json
+```
+
+Now open your dev environment and live a squiggly-free life.
+
 ## `qmk docs`
 
 This command starts a local HTTP server which you can use for browsing or improving the docs. Default port is 8936.

lib/python/qmk/cli/__init__.py

@@ -8,6 +8,7 @@
 
 from . import cformat
 from . import compile
+from . import compiledb
 from . import config
 from . import docs
 from . import doctor

lib/python/qmk/cli/compiledb.py

@@ -0,0 +1,120 @@
+"""Creates a compilation database for the given keyboard build.
+"""
+
+import json
+import re
+import shlex
+import subprocess
+from functools import lru_cache
+from pathlib import Path
+from subprocess import check_output
+from typing import Dict, List, TextIO
+
+from milc import cli
+
+from qmk.commands import create_make_command
+from qmk.constants import QMK_FIRMWARE
+from qmk.decorators import automagic_keyboard, automagic_keymap
+
+
+@lru_cache(maxsize=10)
+def system_libs(binary: str):
+    """Find the system include directory that the given build tool uses.
+
+    Only tested on OSX+homebrew so far.
+    """
+
+    try:
+        return list(Path(check_output(['which', binary]).rstrip().decode()).resolve().parent.parent.glob("*/include"))
+    except Exception:
+        return []
+
+
+file_re = re.compile(r"""printf "Compiling: ([^"]+)""")
+cmd_re = re.compile(r"""LOG=\$\((.+?)\&\&""")
+
+
+def parse_make_n(f: TextIO) -> List[Dict[str, str]]:
+    """parse the output of `make -n <target>`
+
+    This function makes many assumptions about the format of your build log.
+    This happens to work right now for qmk.
+    """
+
+    state = 'start'
+    this_file = None
+    records = []
+    for line in f:
+        if state == 'start':
+            m = file_re.search(line)
+            if m:
+                this_file = m.group(1)
+                state = 'cmd'
+
+        if state == 'cmd':
+            m = cmd_re.search(line)
+            if m:
+                # we have a hit!
+                this_cmd = m.group(1)
+                args = shlex.split(this_cmd)
+                args += ['-I%s' % s for s in system_libs(args[0])]
+                new_cmd = ' '.join(shlex.quote(s) for s in args if s != '-mno-thumb-interwork')
+                records.append({"directory": str(QMK_FIRMWARE.resolve()), "command": new_cmd, "file": this_file})
+                state = 'start'
+
+    return records
+
+
+@cli.argument('-kb', '--keyboard', help='The keyboard to build a firmware for. Ignored when a configurator export is supplied.')
+@cli.argument('-km', '--keymap', help='The keymap to build a firmware for. Ignored when a configurator export is supplied.')
+@cli.subcommand('Create a compilation database.')
+@automagic_keyboard
+@automagic_keymap
+def compiledb(cli):
+    """Creates a compilation database for the given keyboard build.
+
+    Does a make clean, then a make -n for this target and uses the dry-run output to create
+    a compilation database (compile_commands.json). This file can help some IDEs and
+    IDE-like editors work better. For more information about this:
+
+        https://clang.llvm.org/docs/JSONCompilationDatabase.html
+    """
+    command = None
+    # check both config domains: the magic decorator fills in `compiledb` but the user is
+    # more likely to have set `compile` in their config file.
+    current_keyboard = cli.config.compiledb.keyboard or cli.config.compile.keyboard
+    current_keymap = cli.config.compiledb.keymap or cli.config.compile.keymap
+
+    if current_keyboard and current_keymap:
+        # Generate the make command for a specific keyboard/keymap.
+        command = create_make_command(current_keyboard, current_keymap, dry_run=True)
+
+    elif not current_keyboard:
+        cli.log.error('Could not determine keyboard!')
+    elif not current_keymap:
+        cli.log.error('Could not determine keymap!')
+
+    if command:
+        # re-use same executable as the main make invocation (might be gmake)
+        clean_command = [command[0], 'clean']
+        cli.log.info('Making clean with {fg_cyan}%s', ' '.join(clean_command))
+        subprocess.run(clean_command, stdout=subprocess.DEVNULL, stderr=subprocess.DEVNULL)
+
+        cli.log.info('Gathering build instructions from {fg_cyan}%s', ' '.join(command))
+        proc = subprocess.Popen(command, stdout=subprocess.PIPE, stderr=subprocess.PIPE, text=True)
+        db = parse_make_n(proc.stdout)
+        res = proc.wait()
+        if res != 0:
+            raise RuntimeError(f"Got error from: {repr(command)}")
+
+        cli.log.info(f"Found {len(db)} compile commands")
+
+        dbpath = QMK_FIRMWARE / 'compile_commands.json'
+
+        cli.log.info(f"Writing build database to {dbpath}")
+        dbpath.write_text(json.dumps(db, indent=4))
+
+    else:
+        cli.log.error('You must supply both `--keyboard` and `--keymap`, or be in a directory for a keyboard or keymap.')
+        cli.echo('usage: qmk compiledb [-kb KEYBOARD] [-km KEYMAP]')
+        return False

lib/python/qmk/commands.py

@@ -10,7 +10,7 @@
 import qmk.keymap
 
 
-def create_make_command(keyboard, keymap, target=None):
+def create_make_command(keyboard, keymap, target=None, dry_run=False):
     """Create a make compile command
 
     Args:
@@ -24,6 +24,9 @@ def create_make_command(keyboard, keymap, target=None):
         target
             Usually a bootloader.
 
+        dry_run
+            make -n -- don't actually build
+
     Returns:
 
         A command that can be run to make the specified keyboard and keymap
@@ -34,7 +37,10 @@ def create_make_command(keyboard, keymap, target=None):
     if target:
         make_args.append(target)
 
-    return [make_cmd, ':'.join(make_args)]
+    if dry_run:
+        return [make_cmd, '-n', ':'.join(make_args)]
+    else:
+        return [make_cmd, ':'.join(make_args)]
 
 
 def compile_configurator_json(user_keymap, bootloader=None):