feat(repl): interactive line editor — history, cursor editing, tab completion (#392)

CHANGELOG.md

@@ -4,6 +4,22 @@ All notable changes to EigenScript are documented here.
 
 ## [Unreleased]
 
+### Added
+- **Interactive REPL line editor** (#392) — the REPL on a tty now has
+  history (in-memory + `EIGS_HISTORY` file, default
+  `~/.eigenscript_history`, created `0600`), arrow-key cursor editing,
+  Home/End/Delete, Ctrl-A/E/U/K/W/L, Ctrl-C line-and-block cancel, and tab
+  completion over builtins + session bindings (both are env bindings, so
+  one walk covers them). Zero new link dependencies: a raw-termios editor
+  in the new CLI-only `src/repl.c` (ported from the EigenOS console
+  editor), not readline/libedit — the embed/freestanding profiles never
+  see it. Piped/non-tty sessions keep the old fgets loop byte-for-byte
+  (`EIGS_REPL_PLAIN=1` forces it on a tty). Interactive sessions record
+  assignment history from the start, so `prev of x` works on session
+  bindings instead of silently answering from no history. Suite section
+  [42c] drives the editor on a real pty (`tests/test_repl.py`) and pins
+  the piped transcript as a byte-exact golden.
+
 ### Fixed
 - **Four silent-wrong-answer builtin contracts** (#312, #314, #316, #317),
   batch-fixed after the 2026-07 backlog triage:

Makefile

@@ -19,9 +19,14 @@ LDFLAGS := -pie -Wl,-z,relro,-z,now -lm -lpthread
 endif
 
 SRC_DIR := src
-SOURCES := $(SRC_DIR)/eigenscript.c $(SRC_DIR)/lexer.c $(SRC_DIR)/parser.c $(SRC_DIR)/builtins.c $(SRC_DIR)/builtins_tensor.c $(SRC_DIR)/hash.c $(SRC_DIR)/arena.c $(SRC_DIR)/state.c $(SRC_DIR)/strbuf.c $(SRC_DIR)/ext_store.c $(SRC_DIR)/fmt.c $(SRC_DIR)/lint.c $(SRC_DIR)/chunk.c $(SRC_DIR)/compiler.c $(SRC_DIR)/vm.c $(SRC_DIR)/jit.c $(SRC_DIR)/trace.c $(SRC_DIR)/eigs_embed.c $(SRC_DIR)/main.c
+SOURCES := $(SRC_DIR)/eigenscript.c $(SRC_DIR)/lexer.c $(SRC_DIR)/parser.c $(SRC_DIR)/builtins.c $(SRC_DIR)/builtins_tensor.c $(SRC_DIR)/hash.c $(SRC_DIR)/arena.c $(SRC_DIR)/state.c $(SRC_DIR)/strbuf.c $(SRC_DIR)/ext_store.c $(SRC_DIR)/fmt.c $(SRC_DIR)/lint.c $(SRC_DIR)/chunk.c $(SRC_DIR)/compiler.c $(SRC_DIR)/vm.c $(SRC_DIR)/jit.c $(SRC_DIR)/trace.c $(SRC_DIR)/eigs_embed.c $(SRC_DIR)/repl.c $(SRC_DIR)/main.c
 BINARY  := $(SRC_DIR)/eigenscript
 
+# CLI-only translation units: linked into the binary, never into the
+# runtime library (repl.c pulls termios/isatty — banned in the
+# freestanding/embed profile, same footing as main.c).
+CLI_ONLY := $(SRC_DIR)/main.c $(SRC_DIR)/repl.c
+
 FULL_SOURCES := $(SOURCES) $(SRC_DIR)/ext_http.c $(SRC_DIR)/ext_db.c \
                 $(SRC_DIR)/model_io.c $(SRC_DIR)/model_infer.c $(SRC_DIR)/model_train.c
 
@@ -30,7 +35,7 @@ PREFIX  := $(HOME)/.local
 # The LSP links the whole runtime (minus main.c): eigenscript.c calls into
 # the VM/compiler/trace layers, so a hand-picked subset bitrots every time
 # the runtime grows (it had, silently — nothing built this target in CI).
-LSP_SOURCES := $(SRC_DIR)/eigenlsp.c $(filter-out $(SRC_DIR)/main.c,$(SOURCES))
+LSP_SOURCES := $(SRC_DIR)/eigenlsp.c $(filter-out $(CLI_ONLY),$(SOURCES))
 LSP_BINARY  := $(SRC_DIR)/eigenlsp
 
 .PHONY: all build full http gfx lib amalgamation tsan test install install-gfx clean coverage coverage-clean fuzz fuzz-run lsp jit-smoke embed-smoke asan valgrind pgo freestanding-check freestanding-libc-diff print-%
@@ -121,7 +126,7 @@ jit-smoke:
 	$(CC) -Wall -Wextra -O2 -o /tmp/jit_smoke $(SRC_DIR)/jit.c $(SRC_DIR)/jit_smoke.c -lm
 	/tmp/jit_smoke
 
-EMBED_SOURCES := $(filter-out $(SRC_DIR)/main.c,$(SOURCES))
+EMBED_SOURCES := $(filter-out $(CLI_ONLY),$(SOURCES))
 
 # Single-file amalgamation (#397): "copy two files, call eigs_open".
 # build/eigenscript_all.c (self-contained, system headers only) + the public
@@ -266,7 +271,7 @@ coverage: coverage-clean
 # Like the LSP, the fuzz harness links the whole runtime minus main.c —
 # the old hand-picked subset bitrotted when the bytecode VM replaced the
 # tree-walking evaluator (eval_node), leaving `make fuzz` unbuildable.
-FUZZ_SOURCES := $(filter-out $(SRC_DIR)/main.c,$(SOURCES))
+FUZZ_SOURCES := $(filter-out $(CLI_ONLY),$(SOURCES))
 
 fuzz: fuzz/fuzz_stdin.c $(FUZZ_SOURCES)
 	$(CC) -g -fsanitize=address,undefined -o fuzz/fuzz_stdin \

README.md

@@ -58,7 +58,7 @@ Image tags: `:latest`, `:X.Y.Z`, `:X.Y`, `:X` for releases; `:edge` tracks `main
 
 ```bash
 eigenscript program.eigs    # run a script
-eigenscript                 # interactive REPL
+eigenscript                 # interactive REPL (history, arrow keys, tab completion)
 eigenscript --version
 ```
 

build.sh

@@ -9,7 +9,7 @@ VERSION=$(cat ../VERSION)
 # Compiler is overridable (e.g. CC=clang ./build.sh) so CI can exercise
 # more than one toolchain; defaults to gcc.
 CC="${CC:-gcc}"
-SOURCES="eigenscript.c lexer.c parser.c builtins.c builtins_tensor.c hash.c arena.c state.c strbuf.c ext_store.c fmt.c lint.c chunk.c compiler.c vm.c jit.c trace.c eigs_embed.c main.c"
+SOURCES="eigenscript.c lexer.c parser.c builtins.c builtins_tensor.c hash.c arena.c state.c strbuf.c ext_store.c fmt.c lint.c chunk.c compiler.c vm.c jit.c trace.c eigs_embed.c repl.c main.c"
 
 # macOS Intel JIT: enabled via the Mach-O TLV-aware prologue (the JIT
 # now calls eigs_jit_load_eigs_current instead of inlining %fs:
@@ -25,7 +25,8 @@ if [ "$1" = "lsp" ]; then
     # toolchain. Links eigenlsp.c against the runtime (SOURCES minus main.c),
     # minimal extensions, gcc-only like the rest of build.sh. Source list reused
     # from SOURCES above so it can't drift.
-    LSP_SOURCES="${SOURCES/ main.c/} eigenlsp.c"
+    LSP_SOURCES="${SOURCES/ main.c/}"
+    LSP_SOURCES="${LSP_SOURCES/ repl.c/} eigenlsp.c"   # repl.c is CLI-only, like main.c
     $CC -Wall -Wextra -Werror=implicit-function-declaration -O2 -fstack-protector-strong -o eigenlsp $LSP_SOURCES \
         -DEIGENSCRIPT_EXT_HTTP=0 \
         -DEIGENSCRIPT_EXT_MODEL=0 \

src/main.c

@@ -6,6 +6,7 @@
 #include "state.h"
 #include "vm.h"
 #include "trace.h"
+#include "repl.h"
 #if EIGENSCRIPT_EXT_GFX
 void register_gfx_builtins(Env *env);
 #endif
@@ -14,137 +15,8 @@ void register_gfx_builtins(Env *env);
 #define EIGENSCRIPT_VERSION "dev"
 #endif
 
-/* ---- REPL ---- */
-
-static void eigenscript_repl(Env *env) {
-    printf("EigenScript %s\n", EIGENSCRIPT_VERSION);
-    printf("Type 'exit' or Ctrl-D to quit.\n\n");
-
-    char line_buf[4096];
-    strbuf input;
-    strbuf_init(&input);
-    int continuation = 0;
-
-    while (1) {
-        printf(continuation ? "...   " : "eigs> ");
-        fflush(stdout);
-
-        if (!fgets(line_buf, sizeof(line_buf), stdin)) {
-            printf("\n");
-            break;
-        }
-
-        /* Exit commands */
-        if (!continuation) {
-            char *trimmed = line_buf;
-            while (*trimmed == ' ' || *trimmed == '\t') trimmed++;
-            if (strcmp(trimmed, "exit\n") == 0 || strcmp(trimmed, "quit\n") == 0 ||
-                strcmp(trimmed, "exit\r\n") == 0 || strcmp(trimmed, "quit\r\n") == 0) {
-                break;
-            }
-        }
-
-        int len = strlen(line_buf);
-        strbuf_append_n(&input, line_buf, (size_t)len);
-
-        /* Multi-line detection */
-        if (!continuation) {
-            /* Check if line ends with colon (block opener) */
-            char *end = line_buf + len - 1;
-            while (end > line_buf && (*end == '\n' || *end == '\r' || *end == ' ')) end--;
-            if (*end == ':') {
-                continuation = 1;
-                continue;
-            }
-        } else {
-            /* In continuation: blank line or unindented line ends block */
-            char *trimmed = line_buf;
-            while (*trimmed == ' ' || *trimmed == '\t') trimmed++;
-            if (*trimmed == '\n' || *trimmed == '\r' || *trimmed == '\0') {
-                continuation = 0;
-                /* fall through to execute */
-            } else if (line_buf[0] == ' ' || line_buf[0] == '\t') {
-                continue; /* still indented, keep accumulating */
-            } else {
-                continuation = 0;
-                /* unindented non-blank: end of block */
-            }
-        }
-
-        /* Skip empty input */
-        {
-            char *check = input.data;
-            while (*check == ' ' || *check == '\t' || *check == '\n' || *check == '\r') check++;
-            if (*check == '\0') {
-                input.len = 0;
-                input.data[0] = '\0';
-                continue;
-            }
-        }
-
-        /* Tokenize, parse, eval with error recovery */
-        g_parse_errors = 0;
-        TokenList tl = tokenize(input.data);
-        if (g_parse_errors > 0) {
-            free_tokenlist(&tl);
-            input.len = 0;
-            input.data[0] = '\0';
-            continue;
-        }
-
-        ASTNode *ast = parse(&tl);
-        if (g_parse_errors > 0) {
-            free_tokenlist(&tl);
-            input.len = 0;
-            input.data[0] = '\0';
-            continue;
-        }
-
-        g_returning = 0;
-        g_return_val = NULL;
-        g_has_error = 0;   /* don't carry a prior line's error into this one */
-        EigsChunk *repl_chunk = compile_ast(ast, env);
-        if (g_parse_errors > 0) {   /* e.g. an un-encodable jump/loop offset */
-            fprintf(stderr, "%d compile error(s) — line not run\n", g_parse_errors);
-            chunk_free(repl_chunk);
-            free_tokenlist(&tl);
-            free_ast(ast);
-            input.len = 0;
-            input.data[0] = '\0';
-            continue;
-        }
-        Value *result = vm_execute(repl_chunk, env);
-        if (g_exit_requested) {                 /* `exit of N` typed at the REPL */
-            g_has_error = 0;
-            chunk_free(repl_chunk);
-            if (result) val_decref(result);
-            free_tokenlist(&tl);
-            free_ast(ast);
-            break;
-        }
-        /* Chunks are refcounted: drop the creator ref. Functions defined
-         * on this line hold their own refs on their nested chunks. */
-        chunk_free(repl_chunk);
-
-        /* Print non-null results */
-        if (result && result->type != VAL_NULL) {
-            char *s = value_to_string(result);
-            printf("=> %s\n", s);
-            free(s);
-        }
-        if (result) val_decref(result);
-
-        free_tokenlist(&tl);
-        /* Function bodies are cloned (AST fns) or compiled into chunks
-         * (bytecode fns), so the per-line AST is safe to free. */
-        free_ast(ast);
-        input.len = 0;
-        input.data[0] = '\0';
-    }
-    strbuf_free(&input);
-}
-
 /* ---- Main ---- */
+/* The REPL (piped loop + the #392 interactive line editor) lives in repl.c. */
 
 static void set_exe_dir(const char *argv0) {
     char exe_path[4096];