Pre-built custom sql.js for sqliteviz (#62)

* Proof-of-concept pre-built custom sql.js

* Rewrite Makefile as a couple of comprehensible Python scripts

* Add link to a blog post about transitive closure in SQLite

* Remove eval extension -- no much point as it only returns a string

* Consistently use existing Path objects

* Add basic tests scalar functions from extension-functions.c

* Test presence of functions from the rest of built extensions

* Use the same sqlite.com domain

* Add a couple SQLite compile flags that may make it a bit faster

* Add regexpi function test

* Add node about regexpi and REGEXP operator

* Workaround first build failure, rebuild lock file and minor fixes

lib/sql-js/build.py

@@ -0,0 +1,83 @@
+import logging
+import subprocess
+from pathlib import Path
+
+
+cflags = (
+    '-O2',
+    '-DSQLITE_OMIT_LOAD_EXTENSION',
+    '-DSQLITE_DISABLE_LFS',
+    '-DSQLITE_ENABLE_FTS3',
+    '-DSQLITE_ENABLE_FTS3_PARENTHESIS',
+    '-DSQLITE_ENABLE_FTS5',
+    '-DSQLITE_ENABLE_JSON1',
+    '-DSQLITE_THREADSAFE=0',
+    '-DSQLITE_ENABLE_NORMALIZE',
+    '-DSQLITE_EXTRA_INIT=extra_init',
+    '-DSQLITE_DEFAULT_MEMSTATUS=0',
+    '-DSQLITE_USE_ALLOCA',
+)
+emflags = (
+    # Base
+    '--memory-init-file', '0',
+    '-s', 'RESERVED_FUNCTION_POINTERS=64',
+    '-s', 'ALLOW_TABLE_GROWTH=1',
+    '-s', 'SINGLE_FILE=0',
+    # WASM
+    '-s', 'WASM=1',
+    '-s', 'ALLOW_MEMORY_GROWTH=1',
+    # Optimisation
+    '-s', 'INLINING_LIMIT=50',
+    '-O3',
+    '-flto',
+    '--closure', '1',
+    # sql.js
+    '-s', 'EXPORTED_FUNCTIONS=@src/sqljs/exported_functions.json',
+    '-s', 'EXPORTED_RUNTIME_METHODS=@src/sqljs/exported_runtime_methods.json',
+    '--pre-js', 'src/sqljs/api.js',
+)
+
+
+def build(src: Path, dst: Path):
+    out = Path('out')
+    out.mkdir()
+
+    logging.info('Building LLVM bitcode for sqlite3.c')
+    subprocess.check_call([
+        'emcc',
+        *cflags,
+        '-c', src / 'sqlite3.c',
+        '-o', out / 'sqlite3.bc',
+    ])
+    logging.info('Building LLVM bitcode for extension-functions.c')
+    subprocess.check_call([
+        'emcc',
+        *cflags,
+        '-c', src / 'extension-functions.c',
+        '-o', out / 'extension-functions.bc',
+    ])
+
+    logging.info('Building WASM from bitcode')
+    subprocess.check_call([
+        'emcc',
+        *emflags,
+        out / 'sqlite3.bc',
+        out / 'extension-functions.bc',
+        '-o', out / 'sql-wasm.js',
+    ])
+
+    logging.info('Post-processing build and copying to dist')
+    (out / 'sql-wasm.wasm').rename(dst / 'sql-wasm.wasm')
+    with (dst / 'sql-wasm.js').open('w') as f:
+        f.write((src / 'sqljs' / 'shell-pre.js').read_text())
+        f.write((out / 'sql-wasm.js').read_text())
+        f.write((src / 'sqljs' / 'shell-post.js').read_text())
+
+
+if __name__ == '__main__':
+    logging.basicConfig(level='INFO', format='%(asctime)s %(levelname)s %(name)s %(message)s')
+
+    src = Path('src')
+    dst = Path('dist')
+    dst.mkdir()
+    build(src, dst)