From da1749db0ae1fe83775dcbdbe60dea1e14340367 Mon Sep 17 00:00:00 2001
From: Weihang Lo <me@weihanglo.tw>
Date: Mon, 26 Oct 2020 02:40:28 +0800
Subject: [PATCH 01/12] feat(util): print_available_packages

---
 src/cargo/util/mod.rs       |  2 +-
 src/cargo/util/workspace.rs | 40 ++++++++++++++++++++++++++++---------
 2 files changed, 32 insertions(+), 10 deletions(-)

diff --git a/src/cargo/util/mod.rs b/src/cargo/util/mod.rs
index 8bed0b91633..11ac2bae679 100644
--- a/src/cargo/util/mod.rs
+++ b/src/cargo/util/mod.rs
@@ -28,7 +28,7 @@ pub use self::to_semver::ToSemver;
 pub use self::vcs::{existing_vcs_repo, FossilRepo, GitRepo, HgRepo, PijulRepo};
 pub use self::workspace::{
     print_available_benches, print_available_binaries, print_available_examples,
-    print_available_tests,
+    print_available_packages, print_available_tests,
 };
 
 mod canonical_url;
diff --git a/src/cargo/util/workspace.rs b/src/cargo/util/workspace.rs
index fbfe11d8433..7da998938bd 100644
--- a/src/cargo/util/workspace.rs
+++ b/src/cargo/util/workspace.rs
@@ -8,7 +8,7 @@ fn get_available_targets<'a>(
     filter_fn: fn(&Target) -> bool,
     ws: &'a Workspace<'_>,
     options: &'a CompileOptions,
-) -> CargoResult<Vec<&'a Target>> {
+) -> CargoResult<Vec<&'a str>> {
     let packages = options.spec.get_packages(ws)?;
 
     let mut targets: Vec<_> = packages
@@ -19,6 +19,7 @@ fn get_available_targets<'a>(
                 .iter()
                 .filter(|target| filter_fn(target))
         })
+        .map(Target::name)
         .collect();
 
     targets.sort();
@@ -26,7 +27,7 @@ fn get_available_targets<'a>(
     Ok(targets)
 }
 
-fn print_available(
+fn print_available_targets(
     filter_fn: fn(&Target) -> bool,
     ws: &Workspace<'_>,
     options: &CompileOptions,
@@ -38,29 +39,50 @@ fn print_available(
     let mut output = String::new();
     writeln!(output, "\"{}\" takes one argument.", option_name)?;
 
-    if targets.is_empty() {
+    print_availables(output, &targets, plural_name)
+}
+
+fn print_availables(output: String, availables: &[&str], plural_name: &str) -> CargoResult<()> {
+    let mut output = output;
+    if availables.is_empty() {
         writeln!(output, "No {} available.", plural_name)?;
     } else {
         writeln!(output, "Available {}:", plural_name)?;
-        for target in targets {
-            writeln!(output, "    {}", target.name())?;
+        for available in availables {
+            writeln!(output, "    {}", available)?;
         }
     }
     bail!("{}", output)
 }
 
+pub fn print_available_packages(ws: &Workspace<'_>) -> CargoResult<()> {
+    let packages = ws
+        .members()
+        .map(|pkg| pkg.name().as_str())
+        .collect::<Vec<_>>();
+
+    let mut output = String::new();
+    writeln!(
+        output,
+        "\"--package <SPEC>\" requires a SPEC format value.\n\
+        Run `cargo help pkgid` for more infomation about SPEC format."
+    )?;
+
+    print_availables(output, &packages, "packages")
+}
+
 pub fn print_available_examples(ws: &Workspace<'_>, options: &CompileOptions) -> CargoResult<()> {
-    print_available(Target::is_example, ws, options, "--example", "examples")
+    print_available_targets(Target::is_example, ws, options, "--example", "examples")
 }
 
 pub fn print_available_binaries(ws: &Workspace<'_>, options: &CompileOptions) -> CargoResult<()> {
-    print_available(Target::is_bin, ws, options, "--bin", "binaries")
+    print_available_targets(Target::is_bin, ws, options, "--bin", "binaries")
 }
 
 pub fn print_available_benches(ws: &Workspace<'_>, options: &CompileOptions) -> CargoResult<()> {
-    print_available(Target::is_bench, ws, options, "--bench", "benches")
+    print_available_targets(Target::is_bench, ws, options, "--bench", "benches")
 }
 
 pub fn print_available_tests(ws: &Workspace<'_>, options: &CompileOptions) -> CargoResult<()> {
-    print_available(Target::is_test, ws, options, "--test", "tests")
+    print_available_targets(Target::is_test, ws, options, "--test", "tests")
 }

From 60751e4840dc4f52ed369ecfe0b585ba4e5343b5 Mon Sep 17 00:00:00 2001
From: Weihang Lo <me@weihanglo.tw>
Date: Mon, 26 Oct 2020 02:41:28 +0800
Subject: [PATCH 02/12] fix: check `--package`'s value manually

---
 src/cargo/util/command_prelude.rs | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/src/cargo/util/command_prelude.rs b/src/cargo/util/command_prelude.rs
index 6800e00118b..fd6063e7d09 100644
--- a/src/cargo/util/command_prelude.rs
+++ b/src/cargo/util/command_prelude.rs
@@ -8,7 +8,7 @@ use crate::util::restricted_names::is_glob_pattern;
 use crate::util::{paths, toml::TomlProfile, validate_package_name};
 use crate::util::{
     print_available_benches, print_available_binaries, print_available_examples,
-    print_available_tests,
+    print_available_packages, print_available_tests,
 };
 use crate::CargoResult;
 use anyhow::bail;
@@ -52,7 +52,7 @@ pub trait AppExt: Sized {
     }
 
     fn arg_package_spec_simple(self, package: &'static str) -> Self {
-        self._arg(multi_opt("package", "SPEC", package).short("p"))
+        self._arg(optional_multi_opt("package", "SPEC", package).short("p"))
     }
 
     fn arg_package(self, package: &'static str) -> Self {
@@ -498,6 +498,13 @@ pub trait ArgMatchesExt {
 
         if let Some(ws) = workspace {
             self.check_optional_opts(ws, &opts)?;
+        } else if self.is_present_with_zero_values("package") {
+            // As for cargo 0.50.0, this won't occur but if someone sneaks in
+            // we can still provide this informative message for them.
+            anyhow::bail!(
+                "\"--package <SPEC>\" requires a SPEC format value.\n\
+                Run `cargo help pkgid` for more infomation about SPEC format."
+            )
         }
 
         Ok(opts)
@@ -588,6 +595,10 @@ about this warning.";
         workspace: &Workspace<'_>,
         compile_opts: &CompileOptions,
     ) -> CargoResult<()> {
+        if self.is_present_with_zero_values("package") {
+            print_available_packages(workspace)?
+        }
+
         if self.is_present_with_zero_values("example") {
             print_available_examples(workspace, compile_opts)?;
         }

From 4d5a56d7d07b7cfc4a3b24c6444473004b7c9792 Mon Sep 17 00:00:00 2001
From: Weihang Lo <me@weihanglo.tw>
Date: Mon, 26 Oct 2020 02:46:26 +0800
Subject: [PATCH 03/12] test: suggest available packages

---
 .../{list_targets.rs => list_availables.rs}   | 70 ++++++++++++-------
 tests/testsuite/main.rs                       |  2 +-
 2 files changed, 45 insertions(+), 27 deletions(-)
 rename tests/testsuite/{list_targets.rs => list_availables.rs} (64%)

diff --git a/tests/testsuite/list_targets.rs b/tests/testsuite/list_availables.rs
similarity index 64%
rename from tests/testsuite/list_targets.rs
rename to tests/testsuite/list_availables.rs
index 09506f5dbce..7b7bac57ad4 100644
--- a/tests/testsuite/list_targets.rs
+++ b/tests/testsuite/list_availables.rs
@@ -1,13 +1,15 @@
-//! Tests for target filter flags giving suggestions on which targets are available.
+//! Tests for packages/target filter flags giving suggestions on which
+//! packages/targets are available.
 
 use cargo_test_support::project;
 
-const EXAMPLE: u8 = 0x1;
-const BIN: u8 = 0x2;
-const TEST: u8 = 0x4;
-const BENCH: u8 = 0x8;
+const EXAMPLE: u8 = 1 << 0;
+const BIN: u8 = 1 << 1;
+const TEST: u8 = 1 << 2;
+const BENCH: u8 = 1 << 3;
+const PACKAGE: u8 = 1 << 4;
 
-fn list_targets_test(command: &str, targets: u8) {
+fn list_availables_test(command: &str, targets: u8) {
     let full_project = project()
         .file("examples/a.rs", "fn main() { }")
         .file("examples/b.rs", "fn main() { }")
@@ -75,6 +77,22 @@ Available tests:
     test1
     test2
 
+",
+            )
+            .with_status(101)
+            .run();
+    }
+
+    if targets & PACKAGE != 0 {
+        full_project
+            .cargo(&format!("{} -p", command))
+            .with_stderr(
+                "\
+[ERROR] \"--package <SPEC>\" requires a SPEC format value.
+Run `cargo help pkgid` for more infomation about SPEC format.
+Available packages:
+    foo
+
 ",
             )
             .with_status(101)
@@ -141,51 +159,51 @@ No tests available.
 }
 
 #[cargo_test]
-fn build_list_targets() {
-    list_targets_test("build", EXAMPLE | BIN | TEST | BENCH);
+fn build_list_availables() {
+    list_availables_test("build", EXAMPLE | BIN | TEST | BENCH | PACKAGE);
 }
 
 #[cargo_test]
-fn check_list_targets() {
-    list_targets_test("check", EXAMPLE | BIN | TEST | BENCH);
+fn check_list_availables() {
+    list_availables_test("check", EXAMPLE | BIN | TEST | BENCH | PACKAGE);
 }
 
 #[cargo_test]
-fn doc_list_targets() {
-    list_targets_test("doc", BIN);
+fn doc_list_availables() {
+    list_availables_test("doc", BIN | PACKAGE);
 }
 
 #[cargo_test]
-fn fix_list_targets() {
-    list_targets_test("fix", EXAMPLE | BIN | TEST | BENCH);
+fn fix_list_availables() {
+    list_availables_test("fix", EXAMPLE | BIN | TEST | BENCH | PACKAGE);
 }
 
 #[cargo_test]
-fn run_list_targets() {
-    list_targets_test("run", EXAMPLE | BIN);
+fn run_list_availables() {
+    list_availables_test("run", EXAMPLE | BIN);
 }
 
 #[cargo_test]
-fn test_list_targets() {
-    list_targets_test("test", EXAMPLE | BIN | TEST | BENCH);
+fn test_list_availables() {
+    list_availables_test("test", EXAMPLE | BIN | TEST | BENCH | PACKAGE);
 }
 
 #[cargo_test]
-fn bench_list_targets() {
-    list_targets_test("bench", EXAMPLE | BIN | TEST | BENCH);
+fn bench_list_availables() {
+    list_availables_test("bench", EXAMPLE | BIN | TEST | BENCH | PACKAGE);
 }
 
 #[cargo_test]
-fn install_list_targets() {
-    list_targets_test("install", EXAMPLE | BIN);
+fn install_list_availables() {
+    list_availables_test("install", EXAMPLE | BIN);
 }
 
 #[cargo_test]
-fn rustdoc_list_targets() {
-    list_targets_test("rustdoc", EXAMPLE | BIN | TEST | BENCH);
+fn rustdoc_list_availables() {
+    list_availables_test("rustdoc", EXAMPLE | BIN | TEST | BENCH);
 }
 
 #[cargo_test]
-fn rustc_list_targets() {
-    list_targets_test("rustc", EXAMPLE | BIN | TEST | BENCH);
+fn rustc_list_availables() {
+    list_availables_test("rustc", EXAMPLE | BIN | TEST | BENCH);
 }
diff --git a/tests/testsuite/main.rs b/tests/testsuite/main.rs
index 2b1767d41e9..6a32d3b13d6 100644
--- a/tests/testsuite/main.rs
+++ b/tests/testsuite/main.rs
@@ -58,7 +58,7 @@ mod init;
 mod install;
 mod install_upgrade;
 mod jobserver;
-mod list_targets;
+mod list_availables;
 mod local_registry;
 mod locate_project;
 mod lockfile_compat;

From fa522ccec1081ecde6c5b78960f3e35c2b439496 Mon Sep 17 00:00:00 2001
From: Weihang Lo <me@weihanglo.tw>
Date: Tue, 27 Oct 2020 22:03:54 +0800
Subject: [PATCH 04/12] fix: more information when -p value is absent

---
 src/cargo/util/command_prelude.rs  |  5 +++--
 src/cargo/util/workspace.rs        | 34 +++++++++++++++++-------------
 tests/testsuite/list_availables.rs |  8 ++++---
 3 files changed, 27 insertions(+), 20 deletions(-)

diff --git a/src/cargo/util/command_prelude.rs b/src/cargo/util/command_prelude.rs
index fd6063e7d09..e4880f0a2a8 100644
--- a/src/cargo/util/command_prelude.rs
+++ b/src/cargo/util/command_prelude.rs
@@ -502,8 +502,9 @@ pub trait ArgMatchesExt {
             // As for cargo 0.50.0, this won't occur but if someone sneaks in
             // we can still provide this informative message for them.
             anyhow::bail!(
-                "\"--package <SPEC>\" requires a SPEC format value.\n\
-                Run `cargo help pkgid` for more infomation about SPEC format."
+                "\"--package <SPEC>\" requires a SPEC format value, \n\
+                which can be any package ID specifier in the dependency graph.\n\
+                Run `cargo help pkgid` for more information about SPEC format."
             )
         }
 
diff --git a/src/cargo/util/workspace.rs b/src/cargo/util/workspace.rs
index 7da998938bd..3f342994ecc 100644
--- a/src/cargo/util/workspace.rs
+++ b/src/cargo/util/workspace.rs
@@ -39,17 +39,12 @@ fn print_available_targets(
     let mut output = String::new();
     writeln!(output, "\"{}\" takes one argument.", option_name)?;
 
-    print_availables(output, &targets, plural_name)
-}
-
-fn print_availables(output: String, availables: &[&str], plural_name: &str) -> CargoResult<()> {
-    let mut output = output;
-    if availables.is_empty() {
+    if targets.is_empty() {
         writeln!(output, "No {} available.", plural_name)?;
     } else {
         writeln!(output, "Available {}:", plural_name)?;
-        for available in availables {
-            writeln!(output, "    {}", available)?;
+        for target in targets {
+            writeln!(output, "    {}", target)?;
         }
     }
     bail!("{}", output)
@@ -61,16 +56,25 @@ pub fn print_available_packages(ws: &Workspace<'_>) -> CargoResult<()> {
         .map(|pkg| pkg.name().as_str())
         .collect::<Vec<_>>();
 
-    let mut output = String::new();
-    writeln!(
-        output,
-        "\"--package <SPEC>\" requires a SPEC format value.\n\
-        Run `cargo help pkgid` for more infomation about SPEC format."
-    )?;
+    let mut output = "\"--package <SPEC>\" requires a SPEC format value, \
+        which can be any package ID specifier in the dependency graph.\n\
+        Run `cargo help pkgid` for more information about SPEC format.\n\n"
+        .to_string();
 
-    print_availables(output, &packages, "packages")
+    if packages.is_empty() {
+        // This would never happen.
+        // Just in case something regresses we covers it here.
+        writeln!(output, "No packages available.")?;
+    } else {
+        writeln!(output, "Possible packages/workspace members:")?;
+        for package in packages  {
+            writeln!(output, "    {}", package)?;
+        }
+    }
+    bail!("{}", output)
 }
 
+
 pub fn print_available_examples(ws: &Workspace<'_>, options: &CompileOptions) -> CargoResult<()> {
     print_available_targets(Target::is_example, ws, options, "--example", "examples")
 }
diff --git a/tests/testsuite/list_availables.rs b/tests/testsuite/list_availables.rs
index 7b7bac57ad4..2297b9a3690 100644
--- a/tests/testsuite/list_availables.rs
+++ b/tests/testsuite/list_availables.rs
@@ -88,9 +88,11 @@ Available tests:
             .cargo(&format!("{} -p", command))
             .with_stderr(
                 "\
-[ERROR] \"--package <SPEC>\" requires a SPEC format value.
-Run `cargo help pkgid` for more infomation about SPEC format.
-Available packages:
+[ERROR] \"--package <SPEC>\" requires a SPEC format value, \
+which can be any package ID specifier in the dependency graph.
+Run `cargo help pkgid` for more information about SPEC format.
+
+Possible packages/workspace members:
     foo
 
 ",

From 139247e4e63c454e3f14d7aecb86779458422f95 Mon Sep 17 00:00:00 2001
From: Weihang Lo <me@weihanglo.tw>
Date: Wed, 28 Oct 2020 00:30:26 +0800
Subject: [PATCH 05/12] feat: list availables for rustc,rustdoc,run,pkgid

---
 src/bin/cargo/commands/pkgid.rs   | 8 +++++++-
 src/cargo/util/command_prelude.rs | 8 ++++++--
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/src/bin/cargo/commands/pkgid.rs b/src/bin/cargo/commands/pkgid.rs
index 098031dcd29..19a17610f67 100644
--- a/src/bin/cargo/commands/pkgid.rs
+++ b/src/bin/cargo/commands/pkgid.rs
@@ -1,6 +1,7 @@
 use crate::command_prelude::*;
 
 use cargo::ops;
+use cargo::util::print_available_packages;
 
 pub fn cli() -> App {
     subcommand("pkgid")
@@ -14,7 +15,12 @@ pub fn cli() -> App {
 
 pub fn exec(config: &mut Config, args: &ArgMatches<'_>) -> CliResult {
     let ws = args.workspace(config)?;
-    let spec = args.value_of("spec").or_else(|| args.value_of("package"));
+    if !args.is_present("spec") && args.is_present_with_zero_values("package") {
+        print_available_packages(&ws)?
+    }
+    let spec = args.value_of("spec").or_else(|| {
+        args.value_of("package")
+    });
     let spec = ops::pkgid(&ws, spec)?;
     cargo::drop_println!(config, "{}", spec);
     Ok(())
diff --git a/src/cargo/util/command_prelude.rs b/src/cargo/util/command_prelude.rs
index e4880f0a2a8..348aa94a0d2 100644
--- a/src/cargo/util/command_prelude.rs
+++ b/src/cargo/util/command_prelude.rs
@@ -56,7 +56,7 @@ pub trait AppExt: Sized {
     }
 
     fn arg_package(self, package: &'static str) -> Self {
-        self._arg(opt("package", package).short("p").value_name("SPEC"))
+        self._arg(optinal_opt("package", package).short("p").value_name("SPEC"))
     }
 
     fn arg_jobs(self) -> Self {
@@ -220,6 +220,10 @@ pub fn opt(name: &'static str, help: &'static str) -> Arg<'static, 'static> {
     Arg::with_name(name).long(name).help(help)
 }
 
+pub fn optinal_opt(name: &'static str, help: &'static str) -> Arg<'static, 'static> {
+    opt(name, help).min_values(0)
+}
+
 pub fn optional_multi_opt(
     name: &'static str,
     value_name: &'static str,
@@ -502,7 +506,7 @@ pub trait ArgMatchesExt {
             // As for cargo 0.50.0, this won't occur but if someone sneaks in
             // we can still provide this informative message for them.
             anyhow::bail!(
-                "\"--package <SPEC>\" requires a SPEC format value, \n\
+                "\"--package <SPEC>\" requires a SPEC format value, \
                 which can be any package ID specifier in the dependency graph.\n\
                 Run `cargo help pkgid` for more information about SPEC format."
             )

From d91be5a36fec992c9f64c85d2fe8c313444a5d05 Mon Sep 17 00:00:00 2001
From: Weihang Lo <me@weihanglo.tw>
Date: Wed, 28 Oct 2020 00:26:19 +0800
Subject: [PATCH 06/12] test: list availables for rustc,rustdoc,run,pkgid

---
 tests/testsuite/list_availables.rs | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/tests/testsuite/list_availables.rs b/tests/testsuite/list_availables.rs
index 2297b9a3690..b1130c29d45 100644
--- a/tests/testsuite/list_availables.rs
+++ b/tests/testsuite/list_availables.rs
@@ -18,6 +18,7 @@ fn list_availables_test(command: &str, targets: u8) {
         .file("tests/test1.rs", "")
         .file("tests/test2.rs", "")
         .file("src/main.rs", "fn main() { }")
+        .file("Cargo.lock", "") // for `cargo pkgid`
         .build();
 
     if targets & EXAMPLE != 0 {
@@ -182,7 +183,7 @@ fn fix_list_availables() {
 
 #[cargo_test]
 fn run_list_availables() {
-    list_availables_test("run", EXAMPLE | BIN);
+    list_availables_test("run", EXAMPLE | BIN | PACKAGE);
 }
 
 #[cargo_test]
@@ -202,10 +203,15 @@ fn install_list_availables() {
 
 #[cargo_test]
 fn rustdoc_list_availables() {
-    list_availables_test("rustdoc", EXAMPLE | BIN | TEST | BENCH);
+    list_availables_test("rustdoc", EXAMPLE | BIN | TEST | BENCH | PACKAGE);
 }
 
 #[cargo_test]
 fn rustc_list_availables() {
-    list_availables_test("rustc", EXAMPLE | BIN | TEST | BENCH);
+    list_availables_test("rustc", EXAMPLE | BIN | TEST | BENCH | PACKAGE);
+}
+
+#[cargo_test]
+fn pkgid_list_availables() {
+    list_availables_test("pkgid", PACKAGE);
 }

From 73fb1a2db647142fce2dbcbfe27fef75a29a3949 Mon Sep 17 00:00:00 2001
From: Weihang Lo <me@weihanglo.tw>
Date: Wed, 28 Oct 2020 02:43:25 +0800
Subject: [PATCH 07/12] feat: list avaiables for clean,tree,update

---
 src/bin/cargo/commands/clean.rs  | 6 ++++++
 src/bin/cargo/commands/tree.rs   | 6 ++++++
 src/bin/cargo/commands/update.rs | 5 +++++
 3 files changed, 17 insertions(+)

diff --git a/src/bin/cargo/commands/clean.rs b/src/bin/cargo/commands/clean.rs
index 80cd2a98f15..b02af1bb4a9 100644
--- a/src/bin/cargo/commands/clean.rs
+++ b/src/bin/cargo/commands/clean.rs
@@ -1,6 +1,7 @@
 use crate::command_prelude::*;
 
 use cargo::ops::{self, CleanOptions};
+use cargo::util::print_available_packages;
 
 pub fn cli() -> App {
     subcommand("clean")
@@ -18,6 +19,11 @@ pub fn cli() -> App {
 
 pub fn exec(config: &mut Config, args: &ArgMatches<'_>) -> CliResult {
     let ws = args.workspace(config)?;
+
+    if args.is_present_with_zero_values("package") {
+        print_available_packages(&ws)?;
+    }
+
     let opts = CleanOptions {
         config,
         spec: values(args, "package"),
diff --git a/src/bin/cargo/commands/tree.rs b/src/bin/cargo/commands/tree.rs
index b700be93952..10e89cd5ebd 100644
--- a/src/bin/cargo/commands/tree.rs
+++ b/src/bin/cargo/commands/tree.rs
@@ -4,6 +4,7 @@ use anyhow::{bail, format_err};
 use cargo::core::dependency::DepKind;
 use cargo::ops::tree::{self, EdgeKind};
 use cargo::ops::Packages;
+use cargo::util::print_available_packages;
 use cargo::util::CargoResult;
 use std::collections::HashSet;
 use std::str::FromStr;
@@ -176,6 +177,11 @@ subtree of the package given to -p.\n\
     }
 
     let ws = args.workspace(config)?;
+
+    if args.is_present_with_zero_values("package") {
+        print_available_packages(&ws)?;
+    }
+
     let charset = tree::Charset::from_str(args.value_of("charset").unwrap())
         .map_err(|e| anyhow::anyhow!("{}", e))?;
     let opts = tree::TreeOptions {
diff --git a/src/bin/cargo/commands/update.rs b/src/bin/cargo/commands/update.rs
index a887f908f7b..34bab9f757e 100644
--- a/src/bin/cargo/commands/update.rs
+++ b/src/bin/cargo/commands/update.rs
@@ -1,6 +1,7 @@
 use crate::command_prelude::*;
 
 use cargo::ops::{self, UpdateOptions};
+use cargo::util::print_available_packages;
 
 pub fn cli() -> App {
     subcommand("update")
@@ -20,6 +21,10 @@ pub fn cli() -> App {
 pub fn exec(config: &mut Config, args: &ArgMatches<'_>) -> CliResult {
     let ws = args.workspace(config)?;
 
+    if args.is_present_with_zero_values("package") {
+        print_available_packages(&ws)?;
+    }
+
     let update_opts = UpdateOptions {
         aggressive: args.is_present("aggressive"),
         precise: args.value_of("precise"),

From c34774561335559e1e5f0d82d898132e87c45b67 Mon Sep 17 00:00:00 2001
From: Weihang Lo <me@weihanglo.tw>
Date: Wed, 28 Oct 2020 01:33:34 +0800
Subject: [PATCH 08/12] test: list availables for clean,tree,update

---
 tests/testsuite/list_availables.rs | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/tests/testsuite/list_availables.rs b/tests/testsuite/list_availables.rs
index b1130c29d45..6bbbeb160d5 100644
--- a/tests/testsuite/list_availables.rs
+++ b/tests/testsuite/list_availables.rs
@@ -215,3 +215,18 @@ fn rustc_list_availables() {
 fn pkgid_list_availables() {
     list_availables_test("pkgid", PACKAGE);
 }
+
+#[cargo_test]
+fn tree_list_availables() {
+    list_availables_test("tree", PACKAGE);
+}
+
+#[cargo_test]
+fn clean_list_availables() {
+    list_availables_test("clean", PACKAGE);
+}
+
+#[cargo_test]
+fn update_list_availables() {
+    list_availables_test("update", PACKAGE);
+}

From cc6b43753be80c634775bcee4c6c5bb0ea1b10ac Mon Sep 17 00:00:00 2001
From: Weihang Lo <me@weihanglo.tw>
Date: Wed, 28 Oct 2020 02:44:59 +0800
Subject: [PATCH 09/12] feat: check cargo uninstall package opt with empty
 value

---
 src/bin/cargo/commands/uninstall.rs | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/src/bin/cargo/commands/uninstall.rs b/src/bin/cargo/commands/uninstall.rs
index 5d989e1c997..45562c7fffd 100644
--- a/src/bin/cargo/commands/uninstall.rs
+++ b/src/bin/cargo/commands/uninstall.rs
@@ -15,6 +15,14 @@ pub fn cli() -> App {
 
 pub fn exec(config: &mut Config, args: &ArgMatches<'_>) -> CliResult {
     let root = args.value_of("root");
+
+    if args.is_present_with_zero_values("package") {
+        return Err(anyhow::anyhow!(
+            "\"--package <SPEC>\" requires a SPEC format value.\n\
+            Run `cargo help pkgid` for more information about SPEC format."
+        ).into())
+    }
+
     let specs = args
         .values_of("spec")
         .unwrap_or_else(|| args.values_of("package").unwrap_or_default())

From 9d9c321c27f9c1e9c619aaa0a2121df236ec92d2 Mon Sep 17 00:00:00 2001
From: Weihang Lo <me@weihanglo.tw>
Date: Wed, 28 Oct 2020 02:44:23 +0800
Subject: [PATCH 10/12] test: check cargo uninstall package opt with empty
 value

---
 tests/testsuite/install.rs | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/tests/testsuite/install.rs b/tests/testsuite/install.rs
index 014c7ed008a..30bfefec0a0 100644
--- a/tests/testsuite/install.rs
+++ b/tests/testsuite/install.rs
@@ -1181,6 +1181,18 @@ fn uninstall_multiple_and_specifying_bin() {
         .run();
 }
 
+#[cargo_test]
+fn uninstall_with_empty_pakcage_option() {
+    cargo_process("uninstall -p")
+        .with_status(101)
+        .with_stderr("\
+[ERROR] \"--package <SPEC>\" requires a SPEC format value.
+Run `cargo help pkgid` for more information about SPEC format.
+",
+        )
+        .run();
+}
+
 #[cargo_test]
 fn uninstall_multiple_and_some_pkg_does_not_exist() {
     pkg("foo", "0.0.1");

From b9554f37abe4f802dd615a550773105a8b2eb386 Mon Sep 17 00:00:00 2001
From: Weihang Lo <me@weihanglo.tw>
Date: Wed, 28 Oct 2020 02:57:06 +0800
Subject: [PATCH 11/12] rustfmt

---
 src/bin/cargo/commands/pkgid.rs     | 4 +---
 src/bin/cargo/commands/uninstall.rs | 3 ++-
 src/cargo/util/command_prelude.rs   | 6 +++++-
 src/cargo/util/workspace.rs         | 3 +--
 tests/testsuite/install.rs          | 3 ++-
 5 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/src/bin/cargo/commands/pkgid.rs b/src/bin/cargo/commands/pkgid.rs
index 19a17610f67..d81b7d9f619 100644
--- a/src/bin/cargo/commands/pkgid.rs
+++ b/src/bin/cargo/commands/pkgid.rs
@@ -18,9 +18,7 @@ pub fn exec(config: &mut Config, args: &ArgMatches<'_>) -> CliResult {
     if !args.is_present("spec") && args.is_present_with_zero_values("package") {
         print_available_packages(&ws)?
     }
-    let spec = args.value_of("spec").or_else(|| {
-        args.value_of("package")
-    });
+    let spec = args.value_of("spec").or_else(|| args.value_of("package"));
     let spec = ops::pkgid(&ws, spec)?;
     cargo::drop_println!(config, "{}", spec);
     Ok(())
diff --git a/src/bin/cargo/commands/uninstall.rs b/src/bin/cargo/commands/uninstall.rs
index 45562c7fffd..9577becbbdc 100644
--- a/src/bin/cargo/commands/uninstall.rs
+++ b/src/bin/cargo/commands/uninstall.rs
@@ -20,7 +20,8 @@ pub fn exec(config: &mut Config, args: &ArgMatches<'_>) -> CliResult {
         return Err(anyhow::anyhow!(
             "\"--package <SPEC>\" requires a SPEC format value.\n\
             Run `cargo help pkgid` for more information about SPEC format."
-        ).into())
+        )
+        .into());
     }
 
     let specs = args
diff --git a/src/cargo/util/command_prelude.rs b/src/cargo/util/command_prelude.rs
index 348aa94a0d2..5f2a0ad50dc 100644
--- a/src/cargo/util/command_prelude.rs
+++ b/src/cargo/util/command_prelude.rs
@@ -56,7 +56,11 @@ pub trait AppExt: Sized {
     }
 
     fn arg_package(self, package: &'static str) -> Self {
-        self._arg(optinal_opt("package", package).short("p").value_name("SPEC"))
+        self._arg(
+            optinal_opt("package", package)
+                .short("p")
+                .value_name("SPEC"),
+        )
     }
 
     fn arg_jobs(self) -> Self {
diff --git a/src/cargo/util/workspace.rs b/src/cargo/util/workspace.rs
index 3f342994ecc..d261717dc10 100644
--- a/src/cargo/util/workspace.rs
+++ b/src/cargo/util/workspace.rs
@@ -67,14 +67,13 @@ pub fn print_available_packages(ws: &Workspace<'_>) -> CargoResult<()> {
         writeln!(output, "No packages available.")?;
     } else {
         writeln!(output, "Possible packages/workspace members:")?;
-        for package in packages  {
+        for package in packages {
             writeln!(output, "    {}", package)?;
         }
     }
     bail!("{}", output)
 }
 
-
 pub fn print_available_examples(ws: &Workspace<'_>, options: &CompileOptions) -> CargoResult<()> {
     print_available_targets(Target::is_example, ws, options, "--example", "examples")
 }
diff --git a/tests/testsuite/install.rs b/tests/testsuite/install.rs
index 30bfefec0a0..070c39008ae 100644
--- a/tests/testsuite/install.rs
+++ b/tests/testsuite/install.rs
@@ -1185,7 +1185,8 @@ fn uninstall_multiple_and_specifying_bin() {
 fn uninstall_with_empty_pakcage_option() {
     cargo_process("uninstall -p")
         .with_status(101)
-        .with_stderr("\
+        .with_stderr(
+            "\
 [ERROR] \"--package <SPEC>\" requires a SPEC format value.
 Run `cargo help pkgid` for more information about SPEC format.
 ",

From 4b9c503dfb2c3e452e2abb7f07a02a7284bf1001 Mon Sep 17 00:00:00 2001
From: Weihang Lo <me@weihanglo.tw>
Date: Wed, 28 Oct 2020 09:40:09 +0800
Subject: [PATCH 12/12] fix: remove unnecessary arg value existence check

---
 src/bin/cargo/commands/pkgid.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/bin/cargo/commands/pkgid.rs b/src/bin/cargo/commands/pkgid.rs
index d81b7d9f619..3b822355664 100644
--- a/src/bin/cargo/commands/pkgid.rs
+++ b/src/bin/cargo/commands/pkgid.rs
@@ -15,7 +15,7 @@ pub fn cli() -> App {
 
 pub fn exec(config: &mut Config, args: &ArgMatches<'_>) -> CliResult {
     let ws = args.workspace(config)?;
-    if !args.is_present("spec") && args.is_present_with_zero_values("package") {
+    if args.is_present_with_zero_values("package") {
         print_available_packages(&ws)?
     }
     let spec = args.value_of("spec").or_else(|| args.value_of("package"));