From b304de81998ebae035d6092b5394f575f42b6788 Mon Sep 17 00:00:00 2001
From: Alex van de Sandt <avandesa@purdue.edu>
Date: Wed, 1 Jan 2020 01:45:27 -0500
Subject: [PATCH] Rewrite `which` (#1144)

* Detect built-in commands passed as args to `which`

This expands the built-in `which` command to detect nushell commands
that may have the same name as a binary in the path.

* Allow which to interpret multiple arguments

Previously, it would discard any argument besides the first. This allows
`which` to process multiple arguments. It also makes the output a stream
of rows.

* Use map to build the output

* Add boolean column for builtins

* Use macros for entry creation shortcuts

* Process command args and use async_stream

In order to use `ichwh`, I'll need to use async_stream. But in order to
avoid lifetime errors with that, I have to process the command args
before using them. I'll admit I don't fully understand what is going on
with the `args.process(...)` function, but it works.

* Use `ichwh` for path searching

This commit transitions from `which` to `ichwh`. The path search is now
done asynchronously.

* Enable the `--all` flag on `which`

* Make `which` respect external commands

Escaped commands passed to wich (e.g., `which "^ls"`), are now searched
before builtins.

* Fix clippy warnings

This commit resolves two warnings from clippy, in light of #1142.

* Update Cargo.lock to get new `ichwh` version

`ichwh@0.2.1` has support for local paths.

* Add documentation for command
---
 Cargo.lock             | 425 +++++++++++++++++++++++++++++++----------
 Cargo.toml             |   2 +-
 docs/commands/which.md |  72 +++++++
 src/commands/which_.rs | 162 +++++++++++-----
 4 files changed, 514 insertions(+), 147 deletions(-)
 create mode 100644 docs/commands/which.md

diff --git a/Cargo.lock b/Cargo.lock
index 193adb0c86..2023e154db 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -35,9 +35,9 @@ dependencies = [
 
 [[package]]
 name = "anyhow"
-version = "1.0.25"
+version = "1.0.26"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9267dff192e68f3399525901e709a48c1d3982c9c072fa32f2127a0cb0babf14"
+checksum = "7825f6833612eb2414095684fcf6c635becf3ce97fe48cf6421321e93bfbd53c"
 
 [[package]]
 name = "app_dirs"
@@ -72,6 +72,42 @@ version = "0.5.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "cff77d8686867eceff3105329d4698d96c2391c176d5d03adc90c7389162b5b8"
 
+[[package]]
+name = "async-attributes"
+version = "1.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "efd3d156917d94862e779f356c5acae312b08fd3121e792c857d7928c8088423"
+dependencies = [
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "async-std"
+version = "1.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0bf6039b315300e057d198b9d3ab92ee029e31c759b7f1afae538145e6f18a3e"
+dependencies = [
+ "async-attributes",
+ "async-task",
+ "crossbeam-channel 0.4.0",
+ "crossbeam-deque",
+ "crossbeam-utils 0.7.0",
+ "futures-core",
+ "futures-io",
+ "futures-timer 2.0.2",
+ "kv-log-macro",
+ "log",
+ "memchr",
+ "mio",
+ "mio-uds",
+ "num_cpus",
+ "once_cell",
+ "pin-project-lite",
+ "pin-utils",
+ "slab",
+]
+
 [[package]]
 name = "async-stream"
 version = "0.1.2"
@@ -93,6 +129,15 @@ dependencies = [
  "syn",
 ]
 
+[[package]]
+name = "async-task"
+version = "1.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d22dc86693d375d2733b536fd8914bea0fa93adf4b1e6bcbd9c7c500cb62d920"
+dependencies = [
+ "crossbeam-utils 0.7.0",
+]
+
 [[package]]
 name = "atty"
 version = "0.2.13"
@@ -172,7 +217,7 @@ dependencies = [
  "num-bigint",
  "num-integer",
  "num-traits 0.2.10",
- "serde 1.0.103",
+ "serde 1.0.104",
 ]
 
 [[package]]
@@ -182,7 +227,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5753e2a71534719bf3f4e57006c3a4f0d2c672a4b676eec84161f763eca87dbf"
 dependencies = [
  "byteorder",
- "serde 1.0.103",
+ "serde 1.0.104",
 ]
 
 [[package]]
@@ -222,7 +267,7 @@ dependencies = [
  "linked-hash-map 0.5.2",
  "md5",
  "rand",
- "serde 1.0.103",
+ "serde 1.0.104",
  "serde_json",
  "time",
 ]
@@ -236,7 +281,7 @@ dependencies = [
  "lazy_static 1.4.0",
  "memchr",
  "regex-automata",
- "serde 1.0.103",
+ "serde 1.0.104",
 ]
 
 [[package]]
@@ -293,7 +338,7 @@ dependencies = [
  "encoding_rs",
  "log",
  "quick-xml",
- "serde 1.0.103",
+ "serde 1.0.104",
  "zip",
 ]
 
@@ -321,7 +366,7 @@ checksum = "31850b4a4d6bae316f7a09e691c944c28299298837edc0a03f755618c23cbc01"
 dependencies = [
  "num-integer",
  "num-traits 0.2.10",
- "serde 1.0.103",
+ "serde 1.0.104",
  "time",
 ]
 
@@ -398,7 +443,7 @@ dependencies = [
  "lazy_static 1.4.0",
  "nom 4.2.3",
  "rust-ini",
- "serde 1.0.103",
+ "serde 1.0.104",
  "serde-hjson 0.8.2",
  "serde_json",
  "toml 0.4.10",
@@ -461,6 +506,15 @@ dependencies = [
  "crossbeam-utils 0.6.6",
 ]
 
+[[package]]
+name = "crossbeam-channel"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "acec9a3b0b3559f15aee4f90746c4e5e293b701c0f7d3925d24e01645267b68c"
+dependencies = [
+ "crossbeam-utils 0.7.0",
+]
+
 [[package]]
 name = "crossbeam-deque"
 version = "0.7.2"
@@ -487,10 +541,11 @@ dependencies = [
 
 [[package]]
 name = "crossbeam-queue"
-version = "0.2.0"
+version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "dfd6515864a82d2f877b42813d4553292c6659498c9a2aa31bab5a15243c2700"
+checksum = "c695eeca1e7173472a32221542ae469b3e9aac3a4fc81f7696bcad82029493db"
 dependencies = [
+ "cfg-if",
  "crossbeam-utils 0.7.0",
 ]
 
@@ -623,7 +678,7 @@ dependencies = [
  "csv-core",
  "itoa",
  "ryu",
- "serde 1.0.103",
+ "serde 1.0.104",
 ]
 
 [[package]]
@@ -717,7 +772,7 @@ dependencies = [
  "libc",
  "ord_subset",
  "rustc-serialize",
- "serde 1.0.103",
+ "serde 1.0.104",
 ]
 
 [[package]]
@@ -822,9 +877,9 @@ checksum = "a357d28ed41a50f9c765dbfe56cbc04a64e53e5fc58ba79fbc34c10ef3df831f"
 
 [[package]]
 name = "encoding_rs"
-version = "0.8.20"
+version = "0.8.22"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "87240518927716f79692c2ed85bfe6e98196d18c6401ec75355760233a7e12e9"
+checksum = "cd8d03faa7fe0c1431609dfad7bbe827af30f82e1e2ae6f7ee4fca6bd764bc28"
 dependencies = [
  "cfg-if",
 ]
@@ -868,7 +923,7 @@ version = "0.3.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3beee4bc16478a1b26f2e80ad819a52d24745e292f521a63c16eea5f74b7eb60"
 dependencies = [
- "serde 1.0.103",
+ "serde 1.0.104",
 ]
 
 [[package]]
@@ -935,12 +990,43 @@ version = "0.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a06f77d526c1a601b7c4cdd98f54b5eaabffc14d5f2f0296febdc7f357c6d3ba"
 
+[[package]]
+name = "fuchsia-zircon"
+version = "0.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2e9763c69ebaae630ba35f74888db465e49e259ba1bc0eda7d06f4a067615d82"
+dependencies = [
+ "bitflags",
+ "fuchsia-zircon-sys",
+]
+
+[[package]]
+name = "fuchsia-zircon-sys"
+version = "0.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3dcaa9ae7725d12cdb85b3ad99a434db70b468c09ded17e012d86b5c1010f7a7"
+
 [[package]]
 name = "futures"
 version = "0.1.29"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "1b980f2816d6ee8673b6517b52cb0e808a180efc92e5c19d02cdda79066703ef"
 
+[[package]]
+name = "futures"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b6f16056ecbb57525ff698bb955162d0cd03bee84e6241c27ff75c08d8ca5987"
+dependencies = [
+ "futures-channel",
+ "futures-core",
+ "futures-executor",
+ "futures-io",
+ "futures-sink",
+ "futures-task",
+ "futures-util",
+]
+
 [[package]]
 name = "futures-channel"
 version = "0.3.1"
@@ -948,6 +1034,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "fcae98ca17d102fd8a3603727b9259fcf7fa4239b603d2142926189bc8999b86"
 dependencies = [
  "futures-core",
+ "futures-sink",
 ]
 
 [[package]]
@@ -972,6 +1059,17 @@ version = "0.3.0-alpha.19"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b35b6263fb1ef523c3056565fa67b1d16f0a8604ff12b11b08c25f28a734c60a"
 
+[[package]]
+name = "futures-executor"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1e274736563f686a837a0568b478bdabfeaec2dca794b5649b04e2fe1627c231"
+dependencies = [
+ "futures-core",
+ "futures-task",
+ "futures-util",
+]
+
 [[package]]
 name = "futures-executor-preview"
 version = "0.3.0-alpha.19"
@@ -983,6 +1081,12 @@ dependencies = [
  "num_cpus",
 ]
 
+[[package]]
+name = "futures-io"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e676577d229e70952ab25f3945795ba5b16d63ca794ca9d2c860e5595d20b5ff"
+
 [[package]]
 name = "futures-io-preview"
 version = "0.3.0-alpha.19"
@@ -1015,6 +1119,12 @@ dependencies = [
  "futures-util-preview",
 ]
 
+[[package]]
+name = "futures-sink"
+version = "0.3.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "171be33efae63c2d59e6dbba34186fe0d6394fb378069a76dfd80fdcffd43c16"
+
 [[package]]
 name = "futures-sink-preview"
 version = "0.3.0-alpha.19"
@@ -1037,15 +1147,25 @@ dependencies = [
  "pin-utils",
 ]
 
+[[package]]
+name = "futures-timer"
+version = "2.0.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a1de7508b218029b0f01662ed8f61b1c964b3ae99d6f25462d0f55a595109df6"
+
 [[package]]
 name = "futures-util"
 version = "0.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c0d66274fb76985d3c62c886d1da7ac4c0903a8c9f754e8fe0f35a6a6cc39e76"
 dependencies = [
+ "futures-channel",
  "futures-core",
+ "futures-io",
  "futures-macro",
+ "futures-sink",
  "futures-task",
+ "memchr",
  "pin-utils",
  "proc-macro-hack",
  "proc-macro-nested",
@@ -1058,7 +1178,7 @@ version = "0.3.0-alpha.19"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5ce968633c17e5f97936bd2797b6e38fb56cf16a7422319f7ec2e30d3c470e8d"
 dependencies = [
- "futures",
+ "futures 0.1.29",
  "futures-channel-preview",
  "futures-core-preview",
  "futures-io-preview",
@@ -1081,9 +1201,9 @@ dependencies = [
 
 [[package]]
 name = "gethostname"
-version = "0.2.0"
+version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d4ab273ca2a31eb6ca40b15837ccf1aa59a43c5db69ac10c542be342fae2e01d"
+checksum = "e692e296bfac1d2533ef168d0b60ff5897b8b70a4009276834014dd8924cc028"
 dependencies = [
  "libc",
  "winapi 0.3.8",
@@ -1182,7 +1302,7 @@ dependencies = [
  "lazy_static 1.4.0",
  "libc",
  "mach 0.3.2",
- "nix 0.16.0",
+ "nix 0.16.1",
  "pin-utils",
  "uom",
  "winapi 0.3.8",
@@ -1280,7 +1400,7 @@ dependencies = [
  "hex 0.4.0",
  "libc",
  "macaddr",
- "nix 0.16.0",
+ "nix 0.16.1",
 ]
 
 [[package]]
@@ -1345,9 +1465,9 @@ dependencies = [
 
 [[package]]
 name = "hermit-abi"
-version = "0.1.3"
+version = "0.1.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "307c3c9f937f38e3534b1d6447ecf090cafcc9744e4a6360e8b037b2cf5af120"
+checksum = "f629dc602392d3ec14bfc8a09b5e644d7ffd725102b48b81e59f90f2633621d7"
 dependencies = [
  "libc",
 ]
@@ -1384,6 +1504,18 @@ dependencies = [
  "quick-error",
 ]
 
+[[package]]
+name = "ichwh"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2ee706a4af782acda5a05b7641867dd9c93d7f2884f214fbbad009e5752228d1"
+dependencies = [
+ "async-std",
+ "cfg-if",
+ "futures 0.3.1",
+ "thiserror",
+]
+
 [[package]]
 name = "idna"
 version = "0.2.0"
@@ -1416,7 +1548,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "712d7b3ea5827fcb9d4fda14bf4da5f136f0db2ae9c8f4bd4e2d1c6fde4e6db2"
 dependencies = [
  "autocfg",
- "serde 1.0.103",
+ "serde 1.0.104",
 ]
 
 [[package]]
@@ -1430,9 +1562,9 @@ dependencies = [
 
 [[package]]
 name = "inventory"
-version = "0.1.4"
+version = "0.1.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f4cece20baea71d9f3435e7bbe9adf4765f091c5fe404975f844006964a71299"
+checksum = "2bf98296081bd2cb540acc09ef9c97f22b7e487841520350293605db1b2c7a27"
 dependencies = [
  "ctor",
  "ghost",
@@ -1441,9 +1573,9 @@ dependencies = [
 
 [[package]]
 name = "inventory-impl"
-version = "0.1.4"
+version = "0.1.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c2869bf972e998977b1cb87e60df70341d48e48dca0823f534feb91ea44adaf9"
+checksum = "0a8e30575afe28eea36a9a39136b70b2fb6b0dd0a212a5bd1f30a498395c0274"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -1466,7 +1598,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "17b77027f12e53ae59a379f7074259d32eb10867e6183388020e922832d9c3fb"
 dependencies = [
  "bytes",
- "crossbeam-channel",
+ "crossbeam-channel 0.3.9",
  "crossbeam-utils 0.6.6",
  "curl",
  "curl-sys",
@@ -1537,9 +1669,9 @@ dependencies = [
 
 [[package]]
 name = "js-sys"
-version = "0.3.32"
+version = "0.3.33"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1c840fdb2167497b0bd0db43d6dfe61e91637fa72f9d061f8bd17ddc44ba6414"
+checksum = "367647c532db6f1555d7151e619540ec5f713328235b8c062c6b4f63e84adfe3"
 dependencies = [
  "wasm-bindgen",
 ]
@@ -1554,6 +1686,15 @@ dependencies = [
  "winapi-build",
 ]
 
+[[package]]
+name = "kv-log-macro"
+version = "1.0.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8c54d9f465d530a752e6ebdc217e081a7a614b48cb200f6f0aee21ba6bc9aabb"
+dependencies = [
+ "log",
+]
+
 [[package]]
 name = "language-reporting"
 version = "0.4.0"
@@ -1564,7 +1705,7 @@ dependencies = [
  "itertools 0.7.11",
  "log",
  "render-tree",
- "serde 1.0.103",
+ "serde 1.0.104",
  "serde_derive",
  "termcolor",
 ]
@@ -1782,6 +1923,48 @@ dependencies = [
  "adler32",
 ]
 
+[[package]]
+name = "mio"
+version = "0.6.21"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "302dec22bcf6bae6dfb69c647187f4b4d0fb6f535521f7bc022430ce8e12008f"
+dependencies = [
+ "cfg-if",
+ "fuchsia-zircon",
+ "fuchsia-zircon-sys",
+ "iovec",
+ "kernel32-sys",
+ "libc",
+ "log",
+ "miow",
+ "net2",
+ "slab",
+ "winapi 0.2.8",
+]
+
+[[package]]
+name = "mio-uds"
+version = "0.6.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "966257a94e196b11bb43aca423754d87429960a768de9414f3691d6957abf125"
+dependencies = [
+ "iovec",
+ "libc",
+ "mio",
+]
+
+[[package]]
+name = "miow"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8c1f2f3b1cf331de6896aabf6e9d55dca90356cc9960cca7eaaf408a355ae919"
+dependencies = [
+ "kernel32-sys",
+ "net2",
+ "winapi 0.2.8",
+ "ws2_32-sys",
+]
+
 [[package]]
 name = "natural"
 version = "0.3.0"
@@ -1797,11 +1980,22 @@ dependencies = [
  "bincode",
  "cfg-if",
  "log",
- "serde 1.0.103",
+ "serde 1.0.104",
  "serde_derive",
  "wasm-bindgen",
 ]
 
+[[package]]
+name = "net2"
+version = "0.2.33"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "42550d9fb7b6684a6d404d9fa7250c2eb2646df731d1c06afc06dcee9e1bcf88"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "winapi 0.3.8",
+]
+
 [[package]]
 name = "nix"
 version = "0.14.1"
@@ -1830,9 +2024,9 @@ dependencies = [
 
 [[package]]
 name = "nix"
-version = "0.16.0"
+version = "0.16.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "19a8300bf427d432716764070ff70d5b2b7801c958b9049686e6cbd8b06fad92"
+checksum = "dd0eaf8df8bab402257e0a5c17a254e4cc1f72a93588a1ddfb5d356c801aa7cb"
 dependencies = [
  "bitflags",
  "cc",
@@ -1935,7 +2129,7 @@ dependencies = [
  "dirs 2.0.2",
  "dunce",
  "futures-preview",
- "futures-timer",
+ "futures-timer 1.0.3",
  "futures-util",
  "futures_codec",
  "getset",
@@ -1943,6 +2137,7 @@ dependencies = [
  "glob",
  "heim",
  "hex 0.4.0",
+ "ichwh",
  "indexmap",
  "itertools 0.8.2",
  "language-reporting",
@@ -1986,7 +2181,7 @@ dependencies = [
  "roxmltree",
  "rusqlite",
  "rustyline",
- "serde 1.0.103",
+ "serde 1.0.104",
  "serde-hjson 0.9.1",
  "serde_bytes",
  "serde_ini",
@@ -2008,7 +2203,6 @@ dependencies = [
  "umask",
  "unicode-xid",
  "url",
- "which",
 ]
 
 [[package]]
@@ -2016,7 +2210,7 @@ name = "nu-build"
 version = "0.7.0"
 dependencies = [
  "lazy_static 1.4.0",
- "serde 1.0.103",
+ "serde 1.0.104",
  "serde_json",
  "toml 0.5.5",
 ]
@@ -2035,7 +2229,7 @@ dependencies = [
  "nu-source",
  "num-bigint",
  "num-traits 0.2.10",
- "serde 1.0.103",
+ "serde 1.0.104",
  "serde_json",
  "serde_yaml",
  "subprocess",
@@ -2076,7 +2270,7 @@ dependencies = [
  "pretty_assertions",
  "pretty_env_logger",
  "ptree",
- "serde 1.0.103",
+ "serde 1.0.104",
  "shellexpand",
  "termcolor",
  "unicode-xid",
@@ -2093,7 +2287,7 @@ dependencies = [
  "nu-source",
  "nu-value-ext",
  "num-bigint",
- "serde 1.0.103",
+ "serde 1.0.104",
  "serde_json",
 ]
 
@@ -2120,7 +2314,7 @@ dependencies = [
  "num-bigint",
  "num-traits 0.2.10",
  "query_interface",
- "serde 1.0.103",
+ "serde 1.0.104",
  "serde_bytes",
  "serde_json",
  "serde_yaml",
@@ -2140,7 +2334,7 @@ dependencies = [
  "nom_locate",
  "nu-build",
  "pretty",
- "serde 1.0.103",
+ "serde 1.0.104",
  "termcolor",
 ]
 
@@ -2258,7 +2452,7 @@ name = "nu_plugin_ps"
 version = "0.7.0"
 dependencies = [
  "futures-preview",
- "futures-timer",
+ "futures-timer 1.0.3",
  "futures-util",
  "heim",
  "nu-build",
@@ -2347,7 +2541,7 @@ dependencies = [
  "autocfg",
  "num-integer",
  "num-traits 0.2.10",
- "serde 1.0.103",
+ "serde 1.0.104",
 ]
 
 [[package]]
@@ -2548,6 +2742,12 @@ dependencies = [
  "ordermap",
 ]
 
+[[package]]
+name = "pin-project-lite"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f0af6cbca0e6e3ce8692ee19fb8d734b641899e07b68eb73e9bbbd32f1703991"
+
 [[package]]
 name = "pin-utils"
 version = "0.1.0-alpha.4"
@@ -2576,7 +2776,7 @@ dependencies = [
  "byteorder",
  "humantime",
  "line-wrap",
- "serde 1.0.103",
+ "serde 1.0.104",
  "xml-rs",
 ]
 
@@ -2693,7 +2893,7 @@ dependencies = [
  "directories",
  "isatty",
  "petgraph",
- "serde 1.0.103",
+ "serde 1.0.104",
  "serde-value",
  "serde_derive",
  "tint",
@@ -2713,9 +2913,9 @@ checksum = "9274b940887ce9addde99c4eee6b5c44cc494b182b97e73dc8ffdcb3397fd3f0"
 
 [[package]]
 name = "quick-xml"
-version = "0.17.1"
+version = "0.17.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7219717e55033c0c1c2368d6c469baaf10115ffdb54b1e83a8b1e8bfd95cde19"
+checksum = "fe1e430bdcf30c9fdc25053b9c459bb1a4672af4617b6c783d7d91dc17c6bbb0"
 dependencies = [
  "encoding_rs",
  "memchr",
@@ -2825,9 +3025,9 @@ dependencies = [
 
 [[package]]
 name = "rayon"
-version = "1.2.1"
+version = "1.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "43739f8831493b276363637423d3622d4bd6394ab6f0a9c4a552e208aeb7fddd"
+checksum = "db6ce3297f9c85e16621bb8cca38a06779ffc31bb8184e1be4bed2be4678a098"
 dependencies = [
  "crossbeam-deque",
  "either",
@@ -2836,9 +3036,9 @@ dependencies = [
 
 [[package]]
 name = "rayon-core"
-version = "1.6.1"
+version = "1.7.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f8bf17de6f23b05473c437eb958b9c850bfc8af0961fe17b4cc92d5a627b4791"
+checksum = "08a89b46efaf957e52b18062fb2f4660f8b8a4dde1807ca002690868ef2c85a9"
 dependencies = [
  "crossbeam-deque",
  "crossbeam-queue",
@@ -2858,9 +3058,9 @@ dependencies = [
 
 [[package]]
 name = "readkey"
-version = "0.1.5"
+version = "0.1.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d98db94bb4f3e926c8d8186547cd9366d958d753aff5801214d93d38214e8f0f"
+checksum = "86d401b6d6a1725a59f1b4e813275d289dff3ad09c72b373a10a7a8217ba3146"
 
 [[package]]
 name = "redox_syscall"
@@ -3072,9 +3272,9 @@ checksum = "9dad3f759919b92c3068c696c15c3d17238234498bbdcc80f2c469606f948ac8"
 
 [[package]]
 name = "serde"
-version = "1.0.103"
+version = "1.0.104"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1217f97ab8e8904b57dd22eb61cde455fa7446a9c1cf43966066da047c1f3702"
+checksum = "414115f25f818d7dfccec8ee535d76949ae78584fc4f79a6f45a904bf8ab4449"
 dependencies = [
  "serde_derive",
 ]
@@ -3112,7 +3312,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7a663f873dedc4eac1a559d4c6bc0d0b2c34dc5ac4702e105014b8281489e44f"
 dependencies = [
  "ordered-float",
- "serde 1.0.103",
+ "serde 1.0.104",
 ]
 
 [[package]]
@@ -3121,14 +3321,14 @@ version = "0.11.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "325a073952621257820e7a3469f55ba4726d8b28657e7e36653d1c36dc2c84ae"
 dependencies = [
- "serde 1.0.103",
+ "serde 1.0.104",
 ]
 
 [[package]]
 name = "serde_derive"
-version = "1.0.103"
+version = "1.0.104"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a8c6faef9a2e64b0064f48570289b4bf8823b7581f1d6157c1b52152306651d0"
+checksum = "128f9e303a5a29922045a830221b8f78ec74a5f544944f3d5984f8ec3895ef64"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -3142,7 +3342,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "eb236687e2bb073a7521c021949be944641e671b8505a94069ca37b656c81139"
 dependencies = [
  "result",
- "serde 1.0.103",
+ "serde 1.0.104",
  "void",
 ]
 
@@ -3155,7 +3355,7 @@ dependencies = [
  "indexmap",
  "itoa",
  "ryu",
- "serde 1.0.103",
+ "serde 1.0.104",
 ]
 
 [[package]]
@@ -3175,7 +3375,7 @@ checksum = "9ec5d77e2d4c73717816afac02670d5c4f534ea95ed430442cad02e7a6e32c97"
 dependencies = [
  "dtoa",
  "itoa",
- "serde 1.0.103",
+ "serde 1.0.104",
  "url",
 ]
 
@@ -3187,7 +3387,7 @@ checksum = "691b17f19fc1ec9d94ec0b5864859290dff279dbd7b03f017afda54eb36c3c35"
 dependencies = [
  "dtoa",
  "linked-hash-map 0.5.2",
- "serde 1.0.103",
+ "serde 1.0.104",
  "yaml-rust",
 ]
 
@@ -3203,9 +3403,12 @@ dependencies = [
 
 [[package]]
 name = "shellexpand"
-version = "1.0.0"
+version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "de7a5b5a9142fd278a10e0209b021a1b85849352e6951f4f914735c976737564"
+checksum = "3a23aed0018ea07316c7826ade41e551772031cf652805f93ebc922215a44d4a"
+dependencies = [
+ "dirs 1.0.5",
+]
 
 [[package]]
 name = "slab"
@@ -3226,9 +3429,9 @@ dependencies = [
 
 [[package]]
 name = "smallvec"
-version = "1.0.0"
+version = "1.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "4ecf3b85f68e8abaa7555aa5abdb1153079387e60b718283d732f03897fcfc86"
+checksum = "44e59e0c9fa00817912ae6e4e6e3c4fe04455e75699d06eedc7d85917ed8e8f4"
 
 [[package]]
 name = "socket2"
@@ -3332,7 +3535,7 @@ dependencies = [
  "log",
  "mime",
  "mime_guess",
- "serde 1.0.103",
+ "serde 1.0.104",
  "serde_json",
  "serde_urlencoded",
  "url",
@@ -3379,7 +3582,7 @@ dependencies = [
  "onig",
  "plist",
  "regex-syntax",
- "serde 1.0.103",
+ "serde 1.0.104",
  "serde_derive",
  "serde_json",
  "walkdir",
@@ -3454,6 +3657,26 @@ dependencies = [
  "unicode-width",
 ]
 
+[[package]]
+name = "thiserror"
+version = "1.0.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6f357d1814b33bc2dc221243f8424104bfe72dbe911d5b71b3816a2dff1c977e"
+dependencies = [
+ "thiserror-impl",
+]
+
+[[package]]
+name = "thiserror-impl"
+version = "1.0.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "eb2e25d25307eb8436894f727aba8f65d07adf02e5b35a13cebed48bd282bfef"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "thread_local"
 version = "0.3.6"
@@ -3499,7 +3722,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "5090db468dad16e1a7a54c8c67280c5e4b544f3d3e018f0b913b400261f85926"
 dependencies = [
  "bytes",
- "futures",
+ "futures 0.1.29",
  "log",
 ]
 
@@ -3509,7 +3732,7 @@ version = "0.4.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "758664fc71a3a69038656bee8b6be6477d2a6c315a6b81f7081f591bffa4111f"
 dependencies = [
- "serde 1.0.103",
+ "serde 1.0.104",
 ]
 
 [[package]]
@@ -3518,7 +3741,7 @@ version = "0.5.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "01d1404644c8b12b16bfcffa4322403a91a451584daaaa7c28d3152e6cbc98cf"
 dependencies = [
- "serde 1.0.103",
+ "serde 1.0.104",
 ]
 
 [[package]]
@@ -3551,7 +3774,7 @@ dependencies = [
  "erased-serde",
  "inventory",
  "lazy_static 1.4.0",
- "serde 1.0.103",
+ "serde 1.0.104",
  "typetag-impl",
 ]
 
@@ -3713,9 +3936,9 @@ checksum = "b89c3ce4ce14bdc6fb6beaf9ec7928ca331de5df7e5ea278375642a2f478570d"
 
 [[package]]
 name = "wasm-bindgen"
-version = "0.2.55"
+version = "0.2.56"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "29ae32af33bacd663a9a28241abecf01f2be64e6a185c6139b04f18b6385c5f2"
+checksum = "99de4b68939a880d530aed51289a7c7baee154e3ea8ac234b542c49da7134aaf"
 dependencies = [
  "cfg-if",
  "wasm-bindgen-macro",
@@ -3723,9 +3946,9 @@ dependencies = [
 
 [[package]]
 name = "wasm-bindgen-backend"
-version = "0.2.55"
+version = "0.2.56"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1845584bd3593442dc0de6e6d9f84454a59a057722f36f005e44665d6ab19d85"
+checksum = "b58e66a093a7b7571cb76409763c495b8741ac4319ac20acc2b798f6766d92ee"
 dependencies = [
  "bumpalo",
  "lazy_static 1.4.0",
@@ -3743,7 +3966,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "83420b37346c311b9ed822af41ec2e82839bfe99867ec6c54e2da43b7538771c"
 dependencies = [
  "cfg-if",
- "futures",
+ "futures 0.1.29",
  "futures-channel-preview",
  "futures-util-preview",
  "js-sys",
@@ -3754,9 +3977,9 @@ dependencies = [
 
 [[package]]
 name = "wasm-bindgen-macro"
-version = "0.2.55"
+version = "0.2.56"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "87fcc747e6b73c93d22c947a6334644d22cfec5abd8b66238484dc2b0aeb9fe4"
+checksum = "a80f89daea7b0a67b11f6e9f911422ed039de9963dce00048a653b63d51194bf"
 dependencies = [
  "quote",
  "wasm-bindgen-macro-support",
@@ -3764,9 +3987,9 @@ dependencies = [
 
 [[package]]
 name = "wasm-bindgen-macro-support"
-version = "0.2.55"
+version = "0.2.56"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3dc4b3f2c4078c8c4a5f363b92fcf62604c5913cbd16c6ff5aaf0f74ec03f570"
+checksum = "4f9dbc3734ad6cff6b76b75b7df98c06982becd0055f651465a08f769bca5c61"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -3777,15 +4000,15 @@ dependencies = [
 
 [[package]]
 name = "wasm-bindgen-shared"
-version = "0.2.55"
+version = "0.2.56"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ca0b78d6d3be8589b95d1d49cdc0794728ca734adf36d7c9f07e6459508bb53d"
+checksum = "d907984f8506b3554eab48b8efff723e764ddbf76d4cd4a3fe4196bc00c49a70"
 
 [[package]]
 name = "wasm-bindgen-webidl"
-version = "0.2.55"
+version = "0.2.56"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3126356474ceb717c8fb5549ae387c9fbf4872818454f4d87708bee997214bb5"
+checksum = "f85a3825a459cf6a929d03bacb54dca37a614d43032ad1343ef2d4822972947d"
 dependencies = [
  "anyhow",
  "heck",
@@ -3799,9 +4022,9 @@ dependencies = [
 
 [[package]]
 name = "web-sys"
-version = "0.3.32"
+version = "0.3.33"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "98405c0a2e722ed3db341b4c5b70eb9fe0021621f7350bab76df93b09b649bbf"
+checksum = "2fb60433d0dc12c803b9b017b3902d80c9451bab78d27bc3210bf2a7b96593f1"
 dependencies = [
  "anyhow",
  "js-sys",
@@ -3819,16 +4042,6 @@ dependencies = [
  "nom 4.2.3",
 ]
 
-[[package]]
-name = "which"
-version = "3.1.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5475d47078209a02e60614f7ba5e645ef3ed60f771920ac1906d7c1cc65024c8"
-dependencies = [
- "failure",
- "libc",
-]
-
 [[package]]
 name = "widestring"
 version = "0.4.0"
@@ -3888,6 +4101,16 @@ dependencies = [
  "winapi-util",
 ]
 
+[[package]]
+name = "ws2_32-sys"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d59cefebd0c892fa2dd6de581e937301d8552cb44489cdff035c6187cb63fa5e"
+dependencies = [
+ "winapi 0.2.8",
+ "winapi-build",
+]
+
 [[package]]
 name = "x11"
 version = "2.18.1"
diff --git a/Cargo.toml b/Cargo.toml
index e7ed9c5e44..af79cada1f 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -107,7 +107,7 @@ subprocess = "0.1.18"
 pretty-hex = "0.1.1"
 hex = "0.4"
 tempfile = "3.1.0"
-which = "3.1"
+ichwh = "0.2"
 textwrap = {version = "0.11.0", features = ["term_size"]}
 shellexpand = "1.0.0"
 pin-utils = "0.1.0-alpha.4"
diff --git a/docs/commands/which.md b/docs/commands/which.md
new file mode 100644
index 0000000000..667e9db18c
--- /dev/null
+++ b/docs/commands/which.md
@@ -0,0 +1,72 @@
+# which
+
+Finds a program file.
+
+Usage:
+  > which  ...args{flags}
+
+## Parameters
+
+- ...args: the names of the commands to find the path to
+- --all: list all executables
+
+## Examples
+
+`which` finds the location of an executable:
+
+```shell
+/home/bob> which python
+━━━━━━━━┯━━━━━━━━━━━━━━━━━┯━━━━━━━━━
+ arg    │ path            │ builtin
+────────┼─────────────────┼─────────
+ python │ /usr/bin/python │ No
+━━━━━━━━┷━━━━━━━━━━━━━━━━━┷━━━━━━━━━
+/home/bob> which cargo
+━━━━━━━┯━━━━━━━━━━━━━━━━━━━━━━━━━━━━┯━━━━━━━━━
+ arg   │ path                       │ builtin
+───────┼────────────────────────────┼─────────
+ cargo │ /home/bob/.cargo/bin/cargo │ No
+━━━━━━━┷━━━━━━━━━━━━━━━━━━━━━━━━━━━━┷━━━━━━━━━
+```
+
+`which` will identify nushell commands:
+
+```shell
+/home/bob> which ls
+━━━━━┯━━━━━━━━━━━━━━━━━━━━━━━━━━┯━━━━━━━━━
+ arg │ path                     │ builtin
+─────┼──────────────────────────┼─────────
+ ls  │ nushell built-in command │ Yes
+━━━━━┷━━━━━━━━━━━━━━━━━━━━━━━━━━┷━━━━━━━━━
+/home/bob> which which
+━━━━━━━┯━━━━━━━━━━━━━━━━━━━━━━━━━━┯━━━━━━━━━
+ arg   │ path                     │ builtin
+───────┼──────────────────────────┼─────────
+ which │ nushell built-in command │ Yes
+━━━━━━━┷━━━━━━━━━━━━━━━━━━━━━━━━━━┷━━━━━━━━━
+```
+
+Passing the `all` flag identifies all instances of a command or binary
+
+```shell
+/home/bob> which ls --all
+━━━┯━━━━━┯━━━━━━━━━━━━━━━━━━━━━━━━━━┯━━━━━━━━━
+ # │ arg │ path                     │ builtin
+───┼─────┼──────────────────────────┼─────────
+ 0 │ ls  │ nushell built-in command │ Yes
+ 1 │ ls  │ /usr/bin/ls              │ No
+━━━┷━━━━━┷━━━━━━━━━━━━━━━━━━━━━━━━━━┷━━━━━━━━━
+```
+
+`which` will also identify local binaries
+
+```shell
+/home/bob> touch foo
+/home/bob> chmod +x foo
+/home/bob> which ./foo
+━━━━━━━┯━━━━━━━━━━━━━━━┯━━━━━━━━━
+ arg   │ path          │ builtin
+───────┼───────────────┼─────────
+ ./foo │ /home/bob/foo │ No
+━━━━━━━┷━━━━━━━━━━━━━━━┷━━━━━━━━━
+```
diff --git a/src/commands/which_.rs b/src/commands/which_.rs
index 7152e1fc38..2e2773bfd3 100644
--- a/src/commands/which_.rs
+++ b/src/commands/which_.rs
@@ -1,7 +1,9 @@
 use crate::commands::WholeStreamCommand;
 use crate::prelude::*;
+use indexmap::map::IndexMap;
 use nu_errors::ShellError;
-use nu_protocol::{Primitive, Signature, SyntaxShape, UntaggedValue, Value};
+use nu_protocol::{Primitive, ReturnSuccess, Signature, SyntaxShape, UntaggedValue, Value};
+use nu_source::Tagged;
 
 pub struct Which;
 
@@ -11,11 +13,12 @@ impl WholeStreamCommand for Which {
     }
 
     fn signature(&self) -> Signature {
-        Signature::build("which").required(
-            "name",
-            SyntaxShape::Any,
-            "the name of the command to find the path to",
-        )
+        Signature::build("which")
+            .switch("all", "list all executables")
+            .rest(
+                SyntaxShape::String,
+                "the names of the commands to find the path to",
+            )
     }
 
     fn usage(&self) -> &str {
@@ -27,51 +30,120 @@ impl WholeStreamCommand for Which {
         args: CommandArgs,
         registry: &CommandRegistry,
     ) -> Result<OutputStream, ShellError> {
-        which(args, registry)
+        args.process(registry, which)?.run()
     }
 }
 
-pub fn which(args: CommandArgs, registry: &CommandRegistry) -> Result<OutputStream, ShellError> {
-    let args = args.evaluate_once(registry)?;
+/// Shortcuts for creating an entry to the output table
+fn entry(arg: impl Into<String>, path: Value, builtin: bool, tag: Tag) -> Value {
+    let mut map = IndexMap::new();
+    map.insert(
+        "arg".to_string(),
+        UntaggedValue::Primitive(Primitive::String(arg.into())).into_value(tag.clone()),
+    );
+    map.insert("path".to_string(), path);
+    map.insert(
+        "builtin".to_string(),
+        UntaggedValue::Primitive(Primitive::Boolean(builtin)).into_value(tag.clone()),
+    );
 
-    let mut which_out = VecDeque::new();
-    let tag = args.call_info.name_tag.clone();
+    UntaggedValue::row(map).into_value(tag)
+}
 
-    if let Some(v) = &args.call_info.args.positional {
-        if !v.is_empty() {
-            match &v[0] {
-                Value {
-                    value: UntaggedValue::Primitive(Primitive::String(s)),
-                    tag,
-                } => {
-                    if let Ok(ok) = which::which(&s) {
-                        which_out.push_back(
-                            UntaggedValue::Primitive(Primitive::Path(ok)).into_value(tag.clone()),
-                        );
-                    }
-                }
-                Value { tag, .. } => {
-                    return Err(ShellError::labeled_error(
-                        "Expected a filename to find",
-                        "needs a filename",
-                        tag,
-                    ));
+macro_rules! entry_builtin {
+    ($arg:expr, $tag:expr) => {
+        entry(
+            $arg.clone(),
+            UntaggedValue::Primitive(Primitive::String("nushell built-in command".to_string()))
+                .into_value($tag.clone()),
+            true,
+            $tag,
+        )
+    };
+}
+
+macro_rules! entry_path {
+    ($arg:expr, $path:expr, $tag:expr) => {
+        entry(
+            $arg.clone(),
+            UntaggedValue::Primitive(Primitive::Path($path)).into_value($tag.clone()),
+            false,
+            $tag,
+        )
+    };
+}
+
+#[derive(Deserialize, Debug)]
+struct WhichArgs {
+    bin: Tagged<String>,
+    all: bool,
+}
+
+fn which(
+    WhichArgs { bin, all }: WhichArgs,
+    RunnableContext { commands, .. }: RunnableContext,
+) -> Result<OutputStream, ShellError> {
+    let external = bin.starts_with('^');
+    let item = if external {
+        bin.item[1..].to_string()
+    } else {
+        bin.item.clone()
+    };
+
+    if all {
+        let stream = async_stream! {
+            if external {
+                if let Ok(path) = ichwh::which(&item).await {
+                    yield ReturnSuccess::value(entry_path!(item, path.into(), bin.tag.clone()));
                 }
             }
-        } else {
-            return Err(ShellError::labeled_error(
-                "Expected a binary to find",
-                "needs application name",
-                tag,
-            ));
-        }
-    } else {
-        return Err(ShellError::labeled_error(
-            "Expected a binary to find",
-            "needs application name",
-            tag,
-        ));
-    }
 
-    Ok(which_out.to_output_stream())
+            let builtin = commands.has(&item);
+            if builtin {
+                yield ReturnSuccess::value(entry_builtin!(item, bin.tag.clone()));
+            }
+
+            if let Ok(paths) = ichwh::which_all(&item).await {
+                if !builtin && paths.len() == 0 {
+                    yield Err(ShellError::labeled_error(
+                        "Binary not found for argument, and argument is not a builtin",
+                        "not found",
+                        &bin.tag,
+                    ));
+                } else {
+                    for path in paths {
+                        yield ReturnSuccess::value(entry_path!(item, path.into(), bin.tag.clone()));
+                    }
+                }
+            } else {
+                yield Err(ShellError::labeled_error(
+                    "Error trying to find binary for argument",
+                    "error",
+                    &bin.tag,
+                ));
+            }
+        };
+
+        Ok(stream.to_output_stream())
+    } else {
+        let stream = async_stream! {
+            if external {
+                if let Ok(path) = ichwh::which(&item).await {
+                    yield ReturnSuccess::value(entry_path!(item, path.into(), bin.tag.clone()));
+                }
+            } else if commands.has(&item) {
+                yield ReturnSuccess::value(entry_builtin!(item, bin.tag.clone()));
+            } else if let Ok(path) = ichwh::which(&item).await {
+                yield ReturnSuccess::value(entry_path!(item, path.into(), bin.tag.clone()));
+            } else {
+                yield Err(ShellError::labeled_error(
+                    "Binary not found for argument, and argument is not a builtin",
+                    "not found",
+                    &bin.tag,
+                ));
+            }
+        };
+
+        Ok(stream.to_output_stream())
+    }
 }