check wasm-bindgen version if running with target web

Cargo.toml

@@ -24,6 +24,7 @@ log = "0.4.6"
 openssl = { version = '0.10.11', optional = true }
 parking_lot = "0.6"
 reqwest = "0.9.14"
+semver = "0.9.0"
 serde = "1.0.74"
 serde_derive = "1.0.74"
 serde_ignored = "0.0.4"

src/bindgen.rs

@@ -4,8 +4,10 @@ use binary_install::Download;
 use child;
 use command::build::{BuildProfile, Target};
 use failure::{self, ResultExt};
+use install;
 use manifest::CrateData;
-use std::path::Path;
+use semver;
+use std::path::{Path, PathBuf};
 use std::process::Command;
 
 /// Run the `wasm-bindgen` CLI to generate bindings for the current crate's
@@ -38,14 +40,21 @@ pub fn wasm_bindgen_build(
     } else {
         "--typescript"
     };
+    let bindgen_path = bindgen.binary("wasm-bindgen")?;
     let target_arg = match target {
         Target::Nodejs => "--nodejs",
         Target::NoModules => "--no-modules",
-        Target::Web => "--web",
+        Target::Web => {
+            if supports_web_target(&bindgen_path)? {
+                "--web"
+            } else {
+                bail!("Your current version of wasm-bindgen does not support the 'web' target. Please update your project to wasm-bindgen version >= 0.2.39.")
+            }
+        }
         Target::Bundler => "--browser",
     };
-    let bindgen_path = bindgen.binary("wasm-bindgen")?;
-    let mut cmd = Command::new(bindgen_path);
+
+    let mut cmd = Command::new(&bindgen_path);
     cmd.arg(&wasm_path)
         .arg("--out-dir")
         .arg(out_dir)
@@ -70,3 +79,13 @@ pub fn wasm_bindgen_build(
     child::run(cmd, "wasm-bindgen").context("Running the wasm-bindgen CLI")?;
     Ok(())
 }
+
+/// Check if the `wasm-bindgen` dependency is locally satisfied.
+fn supports_web_target(cli_path: &PathBuf) -> Result<bool, failure::Error> {
+    let cli_version = semver::Version::parse(&install::get_cli_version(
+        &install::Tool::WasmBindgen,
+        cli_path,
+    )?)?;
+    let expected_version = semver::Version::parse("0.2.39")?;
+    Ok(cli_version >= expected_version)
+}

src/child.rs

@@ -24,7 +24,7 @@ pub fn new_command(program: &str) -> Command {
     }
 }
 
-/// Run the given command and return its stdout.
+/// Run the given command and return on success.
 pub fn run(mut command: Command, command_name: &str) -> Result<(), Error> {
     info!("Running {:?}", command);
 

src/install/mod.rs

@@ -63,7 +63,7 @@ pub fn download_prebuilt_or_cargo_install(
 }
 
 /// Check if the tool dependency is locally satisfied.
-fn check_version(
+pub fn check_version(
     tool: &Tool,
     path: &PathBuf,
     expected_version: &str,
@@ -75,24 +75,24 @@ fn check_version(
         expected_version.to_string()
     };
 
+    let v = get_cli_version(tool, path)?;
+    info!(
+        "Checking installed `{}` version == expected version: {} == {}",
+        tool, v, &expected_version
+    );
+    Ok(v == expected_version)
+}
+
+/// Fetches the version of a CLI tool
+pub fn get_cli_version(tool: &Tool, path: &PathBuf) -> Result<String, failure::Error> {
     let mut cmd = Command::new(path);
     cmd.arg("--version");
-    child::run_capture_stdout(cmd, tool)
-        .map(|stdout| {
-            stdout
-                .trim()
-                .split_whitespace()
-                .nth(1)
-                .map(|v| {
-                    info!(
-                        "Checking installed `{}` version == expected version: {} == {}",
-                        tool, v, &expected_version
-                    );
-                    Ok(v == expected_version)
-                })
-                .unwrap_or(Ok(false))
-        })
-        .unwrap_or(Ok(false))
+    let stdout = child::run_capture_stdout(cmd, tool)?;
+    let version = stdout.trim().split_whitespace().nth(1);
+    match version {
+        Some(v) => Ok(v.to_string()),
+        None => bail!("Something went wrong! We couldn't determine your version of the wasm-bindgen CLI. We were supposed to set that up for you, so it's likely not your fault! You should file an issue: https://github.com/rustwasm/wasm-pack/issues/new?template=bug_report.md.")
+    }
 }
 
 /// Downloads a precompiled copy of the tool, if available.

src/lib.rs

@@ -9,6 +9,7 @@ extern crate strsim;
 extern crate failure;
 extern crate glob;
 extern crate parking_lot;
+extern crate semver;
 extern crate serde;
 extern crate which;
 #[macro_use]

src/manifest/mod.rs

@@ -368,12 +368,12 @@ impl CrateData {
             .position(|pkg| pkg.name == manifest.package.name)
             .ok_or_else(|| format_err!("failed to find package in metadata"))?;
 
-        return Ok(CrateData {
+        Ok(CrateData {
             data,
             manifest,
             current_idx,
             out_name,
-        });
+        })
     }
 
     /// Read the `manifest_path` file and deserializes it using the toml Deserializer.

tests/all/build.rs

@@ -104,6 +104,54 @@ fn renamed_crate_name_works() {
     fixture.wasm_pack().arg("build").assert().success();
 }
 
+#[test]
+fn dash_dash_web_target_has_error_on_old_bindgen() {
+    let fixture = utils::fixture::Fixture::new();
+    fixture
+        .readme()
+        .file(
+            "Cargo.toml",
+            r#"
+                [package]
+                name = "foo"
+                version = "0.1.0"
+                authors = []
+
+                [lib]
+                crate-type = ["cdylib"]
+                name = 'bar'
+
+                [dependencies]
+                wasm-bindgen = "=0.2.37"
+            "#,
+        )
+        .file(
+            "src/lib.rs",
+            r#"
+                extern crate wasm_bindgen;
+                use wasm_bindgen::prelude::*;
+
+                #[wasm_bindgen]
+                pub fn one() -> u32 { 1 }
+            "#,
+        )
+        .install_local_wasm_bindgen();
+    let cmd = fixture
+        .wasm_pack()
+        .arg("build")
+        .arg("--target")
+        .arg("web")
+        .assert()
+        .failure();
+    let output = String::from_utf8(cmd.get_output().stderr.clone()).unwrap();
+
+    assert!(
+        output.contains("0.2.39"),
+        "Output did not contain '0.2.39', output was {}",
+        output
+    );
+}
+
 #[test]
 fn it_should_build_nested_project_with_transitive_dependencies() {
     let fixture = utils::fixture::transitive_dependencies();