feat: Add dotnet module (#416)

Adds a .NET module, which preferentially parses local/git files to get
the .NET version.

11 files changed, 584 insertions, 25 deletions

diff --git a/.github/workflows/continuous-integration.yml b/.github/workflows/continuous-integration.yml
index 378149053..f202333a3 100644
--- a/.github/workflows/continuous-integration.yml
+++ b/.github/workflows/continuous-integration.yml
@@ -70,7 +70,12 @@ jobs:
       - uses: actions/setup-python@master
         with:
           python-version: "3.6.9"
-      
+
+      # Install dotnet at a fixed version
+      - uses: actions/setup-dotnet@master
+        with:
+          dotnet-version: "2.2.402"
+
       # Run the ignored tests that expect the above setup
       - uses: actions/checkout@master
       - name: Run all tests
@@ -88,6 +93,8 @@ jobs:
       - name: Fix file permissions
         run: chmod -R a+w .
       - name: Build the Docker image
-        run: docker build -f tests/Dockerfile --tag starshipcommand/starship-test --cache-from starshipcommand/starship-test .
+        run:
+          docker build -f tests/Dockerfile --tag starshipcommand/starship-test --cache-from
+          starshipcommand/starship-test .
       - name: Run tests in Docker
         run: docker run --rm -v $(pwd):/src/starship starshipcommand/starship-test
diff --git a/docs/config/README.md b/docs/config/README.md
index 5e2cf8de6..2e087ac66 100644
--- a/docs/config/README.md
+++ b/docs/config/README.md
@@ -91,12 +91,13 @@ prompt_order = [
     "git_state",
     "git_status",
     "package",
+    "dotnet",
+    "golang",
+    "java",
     "nodejs",
+    "python",
     "ruby",
     "rust",
-    "python",
-    "golang",
-    "java",
     "nix_shell",
     "memory_usage",
     "aws",
@@ -317,6 +318,41 @@ it would have been `nixpkgs/pkgs`.
 truncation_length = 8
 ```
 
+## Dotnet
+
+The `dotnet` module shows the relevant version of the .NET Core SDK for the current directory. If
+the SDK has been pinned in the current directory, the pinned version is shown. Otherwise the module
+shows the latest installed version of the SDK.
+
+This module will only be shown in your prompt when one of the following files are present in the
+current directory: `global.json`, `project.json`, `*.sln`, `*.csproj`, `*.fsproj`, `*.xproj`. You'll
+also need the .NET Core command-line tools installed in order to use it correctly.
+
+Internally, this module uses its own mechanism for version detection. Typically it is twice as fast
+as running `dotnet --version`, but it may show an incorrect version if your .NET project has an
+unusual directory layout. If accuracy is more important than speed, you can disable the mechanism by
+setting `heuristic = false` in the module options.
+
+### Options
+
+| Variable    | Default       | Description                                              |
+| ----------- | ------------- | -------------------------------------------------------- |
+| `symbol`    | `"•NET "`     | The symbol used before displaying the version of dotnet. |
+| `style`     | `"bold blue"` | The style for the module.                                |
+| `heuristic` | `true`        | Use faster version detection to keep starship snappy.    |
+| `disabled`  | `false`       | Disables the `dotnet` module.                            |
+
+### Example
+
+```toml
+# ~/.config/starship.toml
+
+[dotnet]
+symbol = "🥅 "
+style = "green"
+heuristic = false
+```
+
 ## Environment Variable
 
 The `env_var` module displays the current value of a selected environment variable.
diff --git a/starship/src/configs/dotnet.rs b/starship/src/configs/dotnet.rs
new file mode 100644
index 000000000..084798c6d
--- /dev/null
+++ b/starship/src/configs/dotnet.rs
@@ -0,0 +1,31 @@
+use crate::config::{ModuleConfig, RootModuleConfig, SegmentConfig};
+
+use ansi_term::{Color, Style};
+use starship_module_config_derive::ModuleConfig;
+
+#[derive(Clone, ModuleConfig)]
+pub struct DotnetConfig<'a> {
+    pub symbol: SegmentConfig<'a>,
+    pub version: SegmentConfig<'a>,
+    pub style: Style,
+    pub heuristic: bool,
+    pub disabled: bool,
+}
+
+impl<'a> RootModuleConfig<'a> for DotnetConfig<'a> {
+    fn new() -> Self {
+        DotnetConfig {
+            symbol: SegmentConfig {
+                value: "•NET ",
+                style: None,
+            },
+            version: SegmentConfig {
+                value: "",
+                style: None,
+            },
+            style: Color::Blue.bold(),
+            heuristic: true,
+            disabled: false,
+        }
+    }
+}
diff --git a/starship/src/configs/mod.rs b/starship/src/configs/mod.rs
index bac18a3f9..dcf8bb009 100644
--- a/starship/src/configs/mod.rs
+++ b/starship/src/configs/mod.rs
@@ -1,4 +1,5 @@
 pub mod battery;
+pub mod dotnet;
 pub mod rust;
 
 use crate::config::{ModuleConfig, RootModuleConfig};
@@ -26,12 +27,16 @@ impl<'a> RootModuleConfig<'a> for StarshipRootConfig<'a> {
                 "git_state",
                 "git_status",
                 "package",
+                // ↓ Toolchain version modules ↓
+                // (Let's keep these sorted alphabetically)
+                "dotnet",
+                "golang",
+                "java",
                 "nodejs",
+                "python",
                 "ruby",
                 "rust",
-                "python",
-                "golang",
-                "java",
+                // ↑ Toolchain version modules ↑
                 "nix_shell",
                 "memory_usage",
                 "aws",
diff --git a/starship/src/module.rs b/starship/src/module.rs
index 8ebb89fd3..d14814eb0 100644
--- a/starship/src/module.rs
+++ b/starship/src/module.rs
@@ -5,6 +5,8 @@ use ansi_term::{ANSIString, ANSIStrings};
 use std::fmt;
 
 // List of all modules
+// Keep these ordered alphabetically.
+// Default ordering is handled in configs/mod.rs
 pub const ALL_MODULES: &[&str] = &[
     "aws",
     #[cfg(feature = "battery")]
@@ -12,6 +14,7 @@ pub const ALL_MODULES: &[&str] = &[
     "character",
     "cmd_duration",
     "directory",
+    "dotnet",
     "env_var",
     "git_branch",
     "git_state",
diff --git a/starship/src/modules/directory.rs b/starship/src/modules/directory.rs
index 4bab47c71..fd9e74fd1 100644
--- a/starship/src/modules/directory.rs
+++ b/starship/src/modules/directory.rs
@@ -122,7 +122,7 @@ fn contract_path(full_path: &Path, top_level_path: &Path, top_level_replacement:
 /// On non-Windows OS, does nothing
 #[cfg(target_os = "windows")]
 fn replace_c_dir(path: String) -> String {
-    return path.replace("C:/", "/c");
+    path.replace("C:/", "/c")
 }
 
 /// Replaces "C://" with "/c/" within a Windows path
diff --git a/starship/src/modules/dotnet.rs b/starship/src/modules/dotnet.rs
new file mode 100644
index 000000000..d63256e56
--- /dev/null
+++ b/starship/src/modules/dotnet.rs
@@ -0,0 +1,314 @@
+use std::ffi::OsStr;
+use std::iter::Iterator;
+use std::ops::Deref;
+use std::path::{Path, PathBuf};
+use std::process::{Command, Stdio};
+use std::str;
+
+use super::{Context, Module};
+use crate::config::RootModuleConfig;
+use crate::configs::dotnet::DotnetConfig;
+
+type JValue = serde_json::Value;
+
+const GLOBAL_JSON_FILE: &str = "global.json";
+const PROJECT_JSON_FILE: &str = "project.json";
+
+/// A module which shows the latest (or pinned) version of the dotnet SDK
+///
+/// Will display if any of the following files are present in
+/// the current directory:
+/// global.json, project.json, *.sln, *.csproj, *.fsproj, *.xproj
+pub fn module<'a>(context: &'a Context) -> Option<Module<'a>> {
+    let dotnet_files = get_local_dotnet_files(context).ok()?;
+    if dotnet_files.is_empty() {
+        return None;
+    }
+
+    let mut module = context.new_module("dotnet");
+    let config = DotnetConfig::try_load(module.config);
+
+    // Internally, this module uses its own mechanism for version detection.
+    // Typically it is twice as fast as running `dotnet --version`.
+    let enable_heuristic = config.heuristic;
+    let version = if enable_heuristic {
+        let repo_root = context
+            .get_repo()
+            .ok()
+            .and_then(|r| r.root.as_ref().map(PathBuf::as_path));
+        estimate_dotnet_version(&dotnet_files, &context.current_dir, repo_root)?
+    } else {
+        get_version_from_cli()?
+    };
+
+    module.set_style(config.style);
+    module.create_segment("symbol", &config.symbol);
+    module.create_segment("version", &config.version.with_value(&version.0));
+
+    Some(module)
+}
+
+fn estimate_dotnet_version<'a>(
+    files: &[DotNetFile<'a>],
+    current_dir: &Path,
+    repo_root: Option<&Path>,
+) -> Option<Version> {
+    let get_file_of_type = |t: FileType| files.iter().find(|f| f.file_type == t);
+
+    // It's important to check for a global.json or a solution file first,
+    // but otherwise we can take any relevant file. We'll take whichever is first.
+    let relevant_file = get_file_of_type(FileType::GlobalJson)
+        .or_else(|| get_file_of_type(FileType::SolutionFile))
+        .or_else(|| files.iter().next())?;
+
+    match relevant_file.file_type {
+        FileType::GlobalJson => {
+            get_pinned_sdk_version_from_file(relevant_file.path).or_else(get_latest_sdk_from_cli)
+        }
+        FileType::SolutionFile => {
+            // With this heuristic, we'll assume that a "global.json" won't
+            // be found in any directory above the solution file.
+            get_latest_sdk_from_cli()
+        }
+        _ => {
+            // If we see a dotnet project, we'll check a small number of neighboring
+            // directories to see if we can find a global.json. Otherwise, assume the
+            // latest SDK is in use.
+            try_find_nearby_global_json(current_dir, repo_root).or_else(get_latest_sdk_from_cli)
+        }
+    }
+}
+
+/// Looks for a `global.json` which may exist in one of the parent directories of the current path.
+/// If there is one present, and it contains valid version pinning information, then return that version.
+///
+/// The following places are scanned:
+///     - The parent of the current directory
+///       (Unless there is a git repository, and the parent is above the root of that repository)
+///     - The root of the git repository
+///       (If there is one)
+fn try_find_nearby_global_json(current_dir: &Path, repo_root: Option<&Path>) -> Option<Version> {
+    let current_dir_is_repo_root = repo_root.map(|r| r == current_dir).unwrap_or(false);
+    let parent_dir = if current_dir_is_repo_root {
+        // Don't scan the parent directory if it's above the root of a git repository
+        None
+    } else {
+        current_dir.parent()
+    };
+
+    // Check the parent directory, or otherwise the repository root, for a global.json
+    let mut check_dirs = parent_dir
+        .iter()
+        .chain(repo_root.iter())
+        .copied() // Copies the reference, not the Path itself
+        .collect::<Vec<&Path>>();
+
+    // The parent directory and repository root may be the same directory,
+    // so avoid checking it twice.
+    check_dirs.dedup();
+
+    check_dirs
+        .iter()
+        // repo_root may be the same as the current directory. We don't need to scan it again.
+        .filter(|&&d| d != current_dir)
+        .filter_map(|d| check_directory_for_global_json(d))
+        // This will lazily evaluate the first directory with a global.json
+        .next()
+}
+
+fn check_directory_for_global_json(path: &Path) -> Option<Version> {
+    let global_json_path = path.join(GLOBAL_JSON_FILE);
+    log::debug!(
+        "Checking if global.json exists at: {}",
+        &global_json_path.display()
+    );
+    if global_json_path.exists() {
+        get_pinned_sdk_version_from_file(&global_json_path)
+    } else {
+        None
+    }
+}
+
+fn get_pinned_sdk_version_from_file(path: &Path) -> Option<Version> {
+    let json_text = crate::utils::read_file(path).ok()?;
+    log::debug!(
+        "Checking if .NET SDK version is pinned in: {}",
+        path.display()
+    );
+    get_pinned_sdk_version(&json_text)
+}
+
+fn get_pinned_sdk_version(json: &str) -> Option<Version> {
+    let parsed_json: JValue = serde_json::from_str(json).ok()?;
+
+    match parsed_json {
+        JValue::Object(root) => {
+            let sdk = root.get("sdk")?;
+            match sdk {
+                JValue::Object(sdk) => {
+                    let version = sdk.get("version")?;
+                    match version {
+                        JValue::String(version_string) => {
+                            let mut buffer = String::with_capacity(version_string.len() + 1);
+                            buffer.push('v');
+                            buffer.push_str(version_string);
+                            Some(Version(buffer))
+                        }
+                        _ => None,
+                    }
+                }
+                _ => None,
+            }
+        }
+        _ => None,
+    }
+}
+
+fn get_local_dotnet_files<'a>(context: &'a Context) -> Result<Vec<DotNetFile<'a>>, std::io::Error> {
+    Ok(context
+        .get_dir_files()?
+        .iter()
+        .filter_map(|p| {
+            get_dotnet_file_type(p).map(|t| DotNetFile {
+                path: p.as_ref(),
+                file_type: t,
+            })
+        })
+        .collect())
+}
+
+fn get_dotnet_file_type(path: &Path) -> Option<FileType> {
+    let file_name_lower = map_str_to_lower(path.file_name());
+
+    match file_name_lower.as_ref().map(|f| f.as_ref()) {
+        Some(GLOBAL_JSON_FILE) => return Some(FileType::GlobalJson),
+        Some(PROJECT_JSON_FILE) => return Some(FileType::ProjectJson),
+        _ => (),
+    };
+
+    let extension_lower = map_str_to_lower(path.extension());
+
+    match extension_lower.as_ref().map(|f| f.as_ref()) {
+        Some("sln") => return Some(FileType::SolutionFile),
+        Some("csproj") | Some("fsproj") | Some("xproj") => return Some(FileType::ProjectFile),
+        _ => (),
+    };
+
+    None
+}
+
+fn map_str_to_lower(value: Option<&OsStr>) -> Option<String> {
+    Some(value?.to_str()?.to_ascii_lowercase())
+}
+
+fn get_version_from_cli() -> Option<Version> {
+    let version_output = match Command::new("dotnet").arg("--version").output() {
+        Ok(output) => output,
+        Err(e) => {
+            log::warn!("Failed to execute `dotnet --version`. {}", e);
+            return None;
+        }
+    };
+    let version = str::from_utf8(version_output.stdout.as_slice())
+        .ok()?
+        .trim();
+
+    let mut buffer = String::with_capacity(version.len() + 1);
+    buffer.push('v');
+    buffer.push_str(version);
+
+    Some(Version(buffer))
+}
+
+fn get_latest_sdk_from_cli() -> Option<Version> {
+    let mut cmd = Command::new("dotnet");
+    cmd.arg("--list-sdks")
+        .stdout(Stdio::piped())
+        .stderr(Stdio::null())
+        .stdin(Stdio::null());
+
+    let exit_code = match cmd.status() {
+        Ok(status) => status,
+        Err(e) => {
+            log::warn!("Failed to execute `dotnet --list-sdks`. {}", e);
+            return None;
+        }
+    };
+
+    if exit_code.success() {
+        let sdks_output = cmd.output().ok()?;
+        fn parse_failed<T>() -> Option<T> {
+            log::warn!("Unable to parse the output from `dotnet --list-sdks`.");
+            None
+        };
+        let latest_sdk = str::from_utf8(sdks_output.stdout.as_slice())
+            .ok()?
+            .lines()
+            .map(str::trim)
+            .filter(|l| !l.is_empty())
+            .last()
+            .or_else(parse_failed)?;
+        let take_until = latest_sdk.find('[').or_else(parse_failed)? - 1;
+        if take_until > 1 {
+            let version = &latest_sdk[..take_until];
+            let mut buffer = String::with_capacity(version.len() + 1);
+            buffer.push('v');
+            buffer.push_str(version);
+            Some(Version(buffer))
+        } else {
+            parse_failed()
+        }
+    } else {
+        // Older versions of the dotnet cli do not support the --list-sdks command
+        // So, if the status code indicates failure, fall back to `dotnet --version`
+        log::warn!(
+            "Received a non-success exit code from `dotnet --list-sdks`. \
+             Falling back to `dotnet --version`.",
+        );
+        get_version_from_cli()
+    }
+}
+
+struct DotNetFile<'a> {
+    path: &'a Path,
+    file_type: FileType,
+}
+
+#[derive(PartialEq)]
+enum FileType {
+    ProjectJson,
+    ProjectFile,
+    GlobalJson,
+    SolutionFile,
+}
+
+struct Version(String);
+
+impl Deref for Version {
+    type Target = String;
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+#[test]
+fn should_parse_version_from_global_json() {
+    let json_text = r#"
+        {
+            "sdk": {
+                "version": "1.2.3"
+            }
+        }
+    "#;
+
+    let version = get_pinned_sdk_version(json_text).unwrap();
+    assert_eq!("v1.2.3", version.0);
+}
+
+#[test]
+fn should_ignore_empty_global_json() {
+    let json_text = "{}";
+
+    let version = get_pinned_sdk_version(json_text);
+    assert!(version.is_none());
+}
diff --git a/starship/src/modules/mod.rs b/starship/src/modules/mod.rs
index d5174ada2..5a0b8ddcb 100644
--- a/starship/src/modules/mod.rs
+++ b/starship/src/modules/mod.rs
@@ -3,6 +3,7 @@ mod aws;
 mod character;
 mod cmd_duration;
 mod directory;
+mod dotnet;
 mod env_var;
 mod git_branch;
 mod git_state;
@@ -31,32 +32,34 @@ use crate::module::Module;
 
 pub fn handle<'a>(module: &str, context: &'a Context) -> Option<Module<'a>> {
     match module {
+        // Keep these ordered alphabetically.
+        // Default ordering is handled in configs/mod.rs
         "aws" => aws::module(context),
+        #[cfg(feature = "battery")]
+        "battery" => battery::module(context),
         "directory" => directory::module(context),
-        "env_var" => env_var::module(context),
         "character" => character::module(context),
-        "nodejs" => nodejs::module(context),
-        "rust" => rust::module(context),
-        "python" => python::module(context),
-        "ruby" => ruby::module(context),
-        "golang" => golang::module(context),
-        "line_break" => line_break::module(context),
-        "package" => package::module(context),
+        "cmd_duration" => cmd_duration::module(context),
+        "dotnet" => dotnet::module(context),
+        "env_var" => env_var::module(context),
         "git_branch" => git_branch::module(context),
         "git_state" => git_state::module(context),
         "git_status" => git_status::module(context),
-        "kubernetes" => kubernetes::module(context),
-        "username" => username::module(context),
-        #[cfg(feature = "battery")]
-        "battery" => battery::module(context),
-        "cmd_duration" => cmd_duration::module(context),
+        "golang" => golang::module(context),
+        "hostname" => hostname::module(context),
         "java" => java::module(context),
         "jobs" => jobs::module(context),
+        "kubernetes" => kubernetes::module(context),
+        "line_break" => line_break::module(context),
+        "memory_usage" => memory_usage::module(context),
         "nix_shell" => nix_shell::module(context),
-        "hostname" => hostname::module(context),
+        "nodejs" => nodejs::module(context),
+        "package" => package::module(context),
+        "python" => python::module(context),
+        "ruby" => ruby::module(context),
+        "rust" => rust::module(context),
         "time" => time::module(context),
-        "memory_usage" => memory_usage::module(context),
-
+        "username" => username::module(context),
         _ => {
             eprintln!("Error: Unknown module {}. Use starship module --list to list out all supported modules.", module);
             None
diff --git a/tests/Dockerfile b/tests/Dockerfile
index 9e93f596b..bb825a089 100644
--- a/tests/Dockerfile
+++ b/tests/Dockerfile
@@ -48,6 +48,19 @@ RUN curl https://pyenv.run | bash \
 # Check that Python was correctly installed
 RUN python --version
 
+# Install Dotnet
+ENV DOTNET_HOME /home/nonroot/dotnet
+ENV DOTNET_SDK_VERSION 2.2.402
+
+RUN mkdir -p "$DOTNET_HOME" \
+    && dotnet_download="$DOTNET_HOME/../dotnet.tar.gz" \
+    && curl -SL --output "$dotnet_download" https://dotnetcli.blob.core.windows.net/dotnet/Sdk/$DOTNET_SDK_VERSION/dotnet-sdk-$DOTNET_SDK_VERSION-linux-x64.tar.gz \
+    && tar -zxf "$dotnet_download" -C "$DOTNET_HOME" \
+    && rm "$dotnet_download"
+
+ENV PATH $DOTNET_HOME:$PATH
+RUN dotnet help
+
 # Create blank project
 RUN USER=nonroot cargo new --bin /src/starship
 WORKDIR /src/starship
diff --git a/tests/testsuite/dotnet.rs b/tests/testsuite/dotnet.rs
new file mode 100644
index 000000000..d395b3846
--- /dev/null
+++ b/tests/testsuite/dotnet.rs
@@ -0,0 +1,146 @@
+use super::common;
+use std::fs::{DirBuilder, OpenOptions};
+use std::io::{self, Error, ErrorKind, Write};
+use std::process::{Command, Stdio};
+use tempfile::TempDir;
+
+#[test]
+#[ignore]
+fn shows_nothing_in_directory_with_zero_relevant_files() -> io::Result<()> {
+    let workspace = create_workspace(false)?;
+    expect_output(&workspace, ".", None)
+}
+
+#[test]
+#[ignore]
+fn shows_latest_in_directory_with_solution() -> io::Result<()> {
+    let workspace = create_workspace(false)?;
+    touch_path(&workspace, "solution.sln", None)?;
+    expect_output(&workspace, ".", Some("•NET v2.2.402"))
+}
+
+#[test]
+#[ignore]
+fn shows_latest_in_directory_with_csproj() -> io::Result<()> {
+    let workspace = create_workspace(false)?;
+    touch_path(&workspace, "project.csproj", None)?;
+    expect_output(&workspace, ".", Some("•NET v2.2.402"))
+}
+
+#[test]
+#[ignore]
+fn shows_latest_in_directory_with_fsproj() -> io::Result<()> {
+    let workspace = create_workspace(false)?;
+    touch_path(&workspace, "project.fsproj", None)?;
+    expect_output(&workspace, ".", Some("•NET v2.2.402"))
+}
+
+#[test]
+#[ignore]
+fn shows_latest_in_directory_with_xproj() -> io::Result<()> {
+    let workspace = create_workspace(false)?;
+    touch_path(&workspace, "project.xproj", None)?;
+    expect_output(&workspace, ".", Some("•NET v2.2.402"))
+}
+
+#[test]
+#[ignore]
+fn shows_latest_in_directory_with_project_json() -> io::Result<()> {
+    let workspace = create_workspace(false)?;
+    touch_path(&workspace, "project.json", None)?;
+    expect_output(&workspace, ".", Some("•NET v2.2.402"))
+}
+
+#[test]
+#[ignore]
+fn shows_pinned_in_directory_with_global_json() -> io::Result<()> {
+    let workspace = create_workspace(false)?;
+    let global_json = make_pinned_sdk_json("1.2.3");
+    touch_path(&workspace, "global.json", Some(&global_json))?;
+    expect_output(&workspace, ".", Some("•NET v1.2.3"))
+}
+
+#[test]
+#[ignore]
+fn shows_pinned_in_project_below_root_with_global_json() -> io::Result<()> {
+    let workspace = create_workspace(false)?;
+    let global_json = make_pinned_sdk_json("1.2.3");
+    touch_path(&workspace, "global.json", Some(&global_json))?;
+    touch_path(&workspace, "project/project.csproj", None)?;
+    expect_output(&workspace, "project", Some("•NET v1.2.3"))
+}
+
+#[test]
+#[ignore]
+fn shows_pinned_in_deeply_nested_project_within_repository() -> io::Result<()> {
+    let workspace = create_workspace(true)?;
+    let global_json = make_pinned_sdk_json("1.2.3");
+    touch_path(&workspace, "global.json", Some(&global_json))?;
+    touch_path(&workspace, "deep/path/to/project/project.csproj", None)?;
+    expect_output(&workspace, "deep/path/to/project", Some("•NET v1.2.3"))
+}
+
+fn create_workspace(is_repo: bool) -> io::Result<TempDir> {
+    let repo_dir = common::new_tempdir()?;
+
+    if is_repo {
+        let mut command = Command::new("git");
+        command
+            .args(&["init", "--quiet"])
+            .stdout(Stdio::null())
+            .stderr(Stdio::null())
+            .stdin(Stdio::null())
+            .current_dir(repo_dir.path());
+
+        if !command.status()?.success() {
+            return Err(Error::from(ErrorKind::Other));
+        }
+    }
+
+    Ok(repo_dir)
+}
+
+fn touch_path(workspace: &TempDir, relative_path: &str, contents: Option<&str>) -> io::Result<()> {
+    let path = workspace.path().join(relative_path);
+
+    DirBuilder::new().recursive(true).create(
+        path.parent()
+            .expect("Expected relative_path to be a file in a directory"),
+    )?;
+
+    let mut file = OpenOptions::new()
+        .write(true)
+        .create(true)
+        .truncate(true)
+        .open(&path)?;
+    write!(file, "{}", contents.unwrap_or(""))
+}
+
+fn make_pinned_sdk_json(version: &str) -> String {
+    let json_text = r#"
+        {
+            "sdk": {
+                "version": "INSERT_VERSION"
+            }
+        }
+    "#;
+    json_text.replace("INSERT_VERSION", version)
+}
+
+fn expect_output(workspace: &TempDir, run_from: &str, contains: Option<&str>) -> io::Result<()> {
+    let run_path = workspace.path().join(run_from);
+    let output = common::render_module("dotnet")
+        .current_dir(run_path)
+        .output()?;
+    let text = String::from_utf8(output.stdout).unwrap();
+
+    // This can be helpful for debugging
+    eprintln!("The dotnet module showed: {}", text);
+
+    match contains {
+        Some(contains) => assert!(text.contains(contains)),
+        None => assert!(text.is_empty()),
+    }
+
+    Ok(())
+}
diff --git a/tests/testsuite/main.rs b/tests/testsuite/main.rs
index 471f5332a..f96eadcfd 100644
--- a/tests/testsuite/main.rs
+++ b/tests/testsuite/main.rs
@@ -4,6 +4,7 @@ mod cmd_duration;
 mod common;
 mod configuration;
 mod directory;
+mod dotnet;
 mod env_var;
 mod git_branch;
 mod git_state;