fix: Improve type safety for browser-compatible modules

[jsejcksn]

This PR fixes the current compiler errors emitted when using browser-compatible TypeScript modules without including the Deno namespace library in compilerOptions.lib.

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There is a link to contributing guidelines toward the end of the Deno repo README, which includes this:

Document and maintain browser compatibility.

If a module is browser compatible, include the following in the JSDoc at the top of the module:

// This module is browser compatible.

Maintain browser compatibility for such a module by either not using the global Deno namespace or feature-testing for it. Make sure any new dependencies are also browser compatible.

This statement is not explicit about type compatibility, but I think it is natural for the type safety of browser-compatible modules to be aligned in the same way.

I searched for all files including the mentioned text using this method:

# cd to repo directory
grep -Rl "This module is browser compatible." .

For each file, I checked the diagnostic output of the compiler for warnings/errors using a browser-compatible TSConfig with Deno. (The TSConfig is presently included in the PR, but can be removed if desired.) If diagnostic messages were emitted for a file, I addressed them in the source. Most of the changes involve modifications to conditional expressions used to determine whether or not a Deno method or property exists.

[kt3k]

For each file, I checked the diagnostic output of the compiler for warnings/errors using a browser-compatible TSConfig with Deno.

I think we need to add a new step in .github/workflows/ci.yaml to check these.

something like:

deno cache --config browser-compat.tsconfig.json _util/os.ts
deno cache --config browser-compat.tsconfig.json fmt/colors.ts
...

[jsejcksn]

I think we need to add a new step in .github/workflows/ci.yaml to check these.

@kt3k This makes sense. Have any ideas on how to programmatically generate the list of matching modules and insert into the workflow file so that manual maintenance is not needed?

[kt3k]

@jsejcksn I guess something like the below might work

grep "This module is browser compatible" . -Rl | xargs deno cache --config browser-compat.tsconfig.json

[jsejcksn]

@kt3k I tried adding a step for type checking, but got an error like this:

error: Expected ';', '}' or <eof> at file:///home/runner/work/deno_std/deno_std/.github/workflows/ci.yml:11:11

At first, I thought it was because the YAML file was matching, too, but even after applying a variation to ignore the ./.github directory, the error persisted.

Feel free to make a code change suggestion or add a commit to this PR if you think you can make it work. This was my last addition before reverting:

- name: Type check browser compatible modules
  run: grep -Rl --exclude-dir=./.github "// This module is browser compatible." . | xargs deno cache --config browser-compat.tsconfig.json

[kt3k]

@jsejcksn Thank you for your contribution! LGTM

[jsejcksn]

@kt3k Thanks for fixing the workflow file